Web comprising fine fiber and reactive, adsorptive or absorptive particulate

ABSTRACT

The assemblies of the invention can comprise a fine fiber layer having dispersed within the fine fiber layer an active particulate material. Fluid that flows through the assemblies of the invention can have any material dispersed or dissolved in the fluid react with, be absorbed by, or adsorbed onto, the active particulate within the nanofiber layer. The structures of the invention can act simply as reactive, absorptive, or adsorptive layers with no filtration properties, or the structures of the invention can be assembled into filters that can filter particulate from a mobile fluid while simultaneously reacting, absorbing, or adsorbing materials from the mobile fluid.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/773,067, filed Feb. 13, 2006, which applicationis hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a web or fiber structure. The filter, elementor medium structures of the invention can act as a reactive, adsorptiveor absorptive layer or in a filtration mode. The structure comprises acollection fiber and a reactive, adsorptive or absorptive particulatethat also acts as an active particulate, active material fiber, spaceror separation means. The particulate can act as an absorbent, adsorbentor reactant.

BACKGROUND OF THE INVENTION

Polymer webs can be made by extrusion, melt spinning, air laid and wetlaid processing, etc. The manufacturing technology of filter structuresis vast for obtaining structures that can separate the particulate loadfrom a mobile fluid stream. Such filtration media include surfaceloading media and depth media in which these media can be produced in avariety of geometric structures. Principles relating to the use of suchmedia are described in Kahlbaugh et al., U.S. Pat. Nos. 5,082,476;5,238,474; 5,364,456 and 5,672,399. In any filter structure containingany arbitrarily selected filtration medium, the filter must remove adefined particle size, and at the same time, have sufficient lifetime tobe economically justifiable in its particulate removing properties.Lifetime is generally considered to be the time between installation andthe time a filter obtains sufficient particulate load such that thepressure drop across the filter is greater than a predetermined level.An increased pressure drop can cause filter bypass, mechanical filterfailure, fluid starvation, or other operating problems. Filtrationefficiency is the characteristic of the filtration media that is relatedto the fraction of the particulate removed from the mobile stream.Efficiency is typically measured by a set test protocol defined below.

Surface loading filter media often comprise dense mats of fiber having anon-woven structure that is placed across the path of a mobile fluidstream. While the mobile fluid stream passes through the structure ofthe formed non-woven fibers, the particulate is typically removed fromthe stream at the filter surface with a certain efficiency and remainson the surface. In contrast to surface loading structures, depth mediatypically include a relatively (compared to surface loading media) thickstructure of fiber having a defined solidity, porosity, layer thicknessand efficiency. Depth media and in particular, gradient density depthmedia are shown in Kahlbaugh et al., U.S. Pat. Nos. 5,082,476; 5,238,474and 5,364,456. In general, depth media act in filtration operations byimpeding the particulate loading in a mobile fluid stream within thefilter layer. As the particulates impinge the depth media fibrousstructure, the particulate remains within the depth media and istypically distributed onto and held with internal fibers and throughoutthe filter volume. In contrast, surface loading media typicallyaccumulate particulate in a surface layer.

Groeger et al., U.S. Pat. No. 5,486,410, teach a fibrous structuretypically made from a bicomponent, core/shell fiber, containing aparticulate material. The particulate comprising an immobilizedfunctional material held in the fiber structure. The functional materialis designed to interact with and modify the fluid stream. Typicalmaterials include silica, zeolite, alumina, molecular sieves, etc. thatcan either react with, or absorb materials, in the fluid stream. Markellet al., U.S. Pat. No. 5,328,758, use a melt blown thermoplastic web anda sorbative material in the web for separation processing. Errede etal., U.S. Pat. No. 4,460,642, teach a composite sheet of PTFE that iswater swellable and contains hydrophilic absorptive particles. Thissheet is useful as a wound dressing, as a material for absorbing andremoving non-aqueous solvents, or as a separation chromatographicmaterial. Kolpin et al., U.S. Pat. No. 4,429,001, teach a sorbent sheetcomprising a melt blown fiber containing super absorbent polymerparticles. Deodorizing or air purifying filters are shown in, forexample, Mitsutoshi et al., JP 7265640 and Eiichiro et al., JP 10165731.

Many mobile fluid phases, including both gas and liquid phases, containundesirable components suspended, dissolved, or otherwise entrainedwithin the mobile phase. Such undesirable components may be chemicallyreactive or may be absorbable or adsorbable through the use ofabsorbents or adsorbents. Often these species form a phase that is fullymiscible in the fluid and cannot be filtered, but can be removed only bychemical reaction absorbents or adsorbents. Examples of such materialsare acidic or basic reacting compounds. Acid compounds include hydrogensulfide, sulfur dioxide and other such species basic components includeammonia, amines, quaternary compounds and others. Further reactive gasessuch as Cl₂, SO₂, cyanide, phosgene and others can pose hazards. Lastly,a number of other compounds are objectionable due to odor, color orother undesirable properties. The removal of all such materials from afluid phase, if possible, can be helpful in many end uses. The activelayers of existing systems suffer from problems relating to themechanical instability of the particulate in the layers. In manystructures the particulate is not mechanically fixed in the layer andcan be dislodged easily. In many structures, the amount of activematerials available is limited by the nature of the substrate and theamounts of active material that can be loaded.

While both surface loading media and depth media have been used in thepast and have obtained certain levels of performance, a substantial needremains in the industry for fluid phase treatment and filtration mediathat can provide new and different performance characteristics thanformerly obtained. In particular, a need for improved efficiency,low-pressure drop and excellent adsorptive, absorptive, or reactiveproperties are needed in a structure with high activity and robustmechanical stability.

SUMMARY OF THE INVENTION

The web, filter, or other flow-through or flow-by structure of theinvention can comprise a substantially continuous fine fiber mass orlayer containing the particulate of the invention. A reactive,absorptive, or adsorptive fiber spacer or separation means in the formof a particle can be combined with, or otherwise dispersed in, the fibermass. The web of the invention includes a fiber web or layer and a fiberseparation means or fiber spacer means adhered to the fiber that can beused in the form of a reactive, absorbent, or adsorbent structure.

In one aspect, the web comprises a continuous fibrous structure with acontinuous fiber phase and a reactive, absorptive, or adsorptive activeparticulate that can treat a fluid stream. The fluid stream can be agas, or liquid with entrained materials. The entrained materials can besoluble or insoluble in the mobile fluids and can be particulates ofeither liquid or solid impurities. The liquids can be exemplified byaqueous solutions, nonaqueous fluids, water, oils, and mixtures thereof.

In a second aspect a similar structure can also act as a filter. Theactive particulate comprises a particulate phase dispersed with thefiber. The filter can be used to filter a mobile fluid such as a gaseousstream or a liquid stream. The filter can be used to remove impuritiesfrom the liquid stream or from the gaseous stream. Such impurities canbe entrained particulates. The flow through and flow by structures canbe used in structures that need no PTFE, stretched expanded Teflon® orother related porous fluoropolymer components for successful activity.

By dispersed, is meant that the active particulate is adhered to thefiber, held within a void space within the web or in a pocketpenetrating partially into the web creating a space in the web surface.Once formed, the media comprising the fine fiber layer containing theactive particulate of the invention can be combined with a media layer.That form can be used in a flow-by treatment unit or used in aflow-through filtration unit having adsorptive/absorptive or reactiveproperties. In a flow-by or pass-through unit, the media is simplyconfigured in a form through which the mobile fluid can pass unimpededby any filtration layer and simply contact the absorptive/adsorptive orreactive species formed in the fine fiber layer adjacent to the flowpath of the fluid media. Alternatively, the fine fiber layer containingthe active particulate and media can be formed in a flow-throughfiltration structure that can remove particulate from the mobile fluidwhile in the infiltration mode, the media of the invention can, in afiltration mode, remove the entrained particulate from mobile fluid andat the same time absorb, adsorb or chemically react with unwantedmaterials in the fluid phase that may or may not be in a particulateform.

The term filter refers to the structure that is actually used intreating a mobile fluid. A “filter” usually includes a housing with aninlet and outlet. The term “element” typically refers to a structureused in a filter assembly the includes a media layer and other partsresulting in a useful structurally stable unit that can be inserted andremoved from the filter structure. Elements or webs of the inventioninclude media layer that comprises a particulate dispersed throughout afine fiber web. The combined fine fiber and particulate can be formed ona substrate layer to form a filter medium.

The particulate can comprise an amount of a single type of particulateor blend of dissimilar particles. For example, an active particulate canbe blended with an inert particulate for use in such a layer. The inertparticulate can comprise a single particulate or can be a blend of inertparticulate that differs by composition particle size, particlemorphology or some other particle aspect. Similarly, the activeparticulate can comprise a mixture of particulates including differentactive particulates. For example, a carbon particulate could be blendedwith a zeolite particulate. Alternatively, a carboxy methyl celluloseparticulate can be blended with an ion exchange resin particulate in anactive layer. Further, such active particulate can have a blendedparticulate in the sense that particulates of different size, shape ormethodology can be combined in the active layers of the invention. Theterm “entrained particulate refers to impurities in the mobile fluidwhile the term “dispersed particulate” refers to the particulatedeliberately included within the fiber layers of the invention.

The element of the invention can be used in one of two separate modes.These modes are designated as “flow-through” or “flow-by”. In theflow-through mode, the mobile fluid, liquid or gas, passes through thefine fiber layer and substrate in a filtration mode in a flowsubstantially normal to the plane of the fiber layer. The entrainedparticulate can encounter and be removed by the element and as the fluidpasses through the layers in contact with the particulate, theparticulate can react with absorbed or adsorbed chemical materialssuspended or dissolved in the fluid.

In the flow-by mode, the fluid path is generally parallel to the planeof the fine fiber layer or element surface. In the flow-by mode, thefluid contacts the surface of the layer and does not substantially flowthrough the element. While depending on viscosity, flow rate,temperature, element configuration, the fluid can to some degreepenetrate the layer and can flow from layer to layer, the primary modeof transport of the fluid is bypassing the layer in a directionsubstantially parallel to the layer's surface. In such a mode, theliquid can contact the surface of the layer and chemical materialsdissolved and suspended in the fluid can react with, be absorbed, oradsorbed by the particulate.

The flow-through and flow-by element can be used in a variety offormats. Flow-through element can be used in conventional filterstructures including cartridge panel in some other filter structures,with the element in a pleated or unpleated mode. Similarly, the flow-bymedia can be included in the panel and cartridge structures.

One preferred mode of use of the flow-by material is in a rolled media.Rolled media are prepared by first forming the fine fiber andparticulate layer by heat treating the fiber layer if needed and thenrolling the element into a multi-layered roll having anywhere from 2 to50 layers. The thickness of the roll, or a separation between thelayers, determines the flow rate of fluid through the structure. Theflow rates can be improved by introducing channels into the rolledmedia. Such channels can be preformed in the substrate upon which thefine fiber is spun, or the channels can be formed into the element afterthe fine fiber layer is formed on the substrate and then heat treated ifnecessary. Mechanical forms or spacers can be included with theprocessing steps. The forms or spacers can introduce the channel intothe structure. At least one spacer portion can be included with therolled material to inherently form a channel in one portion of therolled structure. Further, additional spacers can be placed such thateach layer of the rolled structure has at least one channel portion. Anarbitrary number of spacers can be used. At least one spacer per layercan be used up to 5, 10 or 20 spacers per layer. After the spacer layersform a channel in the element, the spacers can be removed. The spacerscan be removed in one mode by unrolling the element and physicallyremoving the spacers from the element. However, in another mode, thespacers can be simply washed from the rolled assembly using a solvent inwhich the spacer (but not the substrate fine fiber or particulate) issoluble, thus removing the spacers and leaving flow-through channelstructures. The spacers can be configured in virtually any shape orstructure as long as the spacer can provide a channel from the first endof the roll to the second end of the roll providing a flow through pathfor fluid. Preferably the dimensions of the channel are greater thanabout 1 mm in major dimension and can range from about 1 to 500 mm inmajor dimension. The profile of the channels can be round, oval,circular, rectangular, square, triangular, or other cross-sectionalprofile. The profile can be regular, or it can be irregular andamorphous. Further along the channel, the cross-sectional profile of thechannel can vary from one end to the other. For example, at the intakeend of the rolled structure, the channel can have a relatively largecross-sectional area, whereas at the opposite end the cross-sectionalarea can be smaller than the input end. Additionally the input end canbe smaller in cross-sectional area than the output end. Any othervariation in size of the spacer can increase turbulence in the flowresulting in improved contact between the fluid and the particulate.

The filter or flow-through or flow-by structures of the invention areuniquely suited to provide useful properties. The flow-through structurecan be used to absorb/adsorb or chemically react with mobile fluidphases that flow through the flow-through structures. The dispersedparticulate within the flow-through structures can react with the mobilefluid (either liquid or gas), or absorb/adsorb, or react withintervening material within the fluid stream. The flow-throughstructures can act both as a filter, and as a structure that can reactwith, absorb, or adsorb materials in the fluid stream. Accordingly, thedual function flow-through structures can remove undesired particulatethat is typically an insoluble phase in the fluid stream. In addition,the flow-through structures can also react with, absorb, or adsorbinsoluble and soluble components of the fluid stream.

A particularly important fluid stream for the application includes airstreams that can contain contaminates such as dust particulate, water,solvent residue, oil residue, mixed aqueous oil residue, harmful gasessuch as chlorine, benzene, sulfur dioxide, etc. Other typical liquidmobile phases include fuel, oils, solvents streams, etc. Such streamscan be contacted with the flow-through structures of the invention toremove water, particulate contaminates, color-forming species, and minoramounts of soluble impurities. In many cases, the streams (both gaseousand liquid) can be contaminated by biological products including prions,viruses, bacteria, spores, DNA segments and other potentially harmfulbiological products or hazardous materials.

The active web or element of the invention can contain the fine fiberlayer with the particulate dispersed within the fiber layer toabsorb/adsorb or react with materials entrained in the mobile fluidphase. Such an element or web can be combined with other active orreactive species in a variety of forms. The particulate of the inventioncan be discrete particles separate from the fiber or the particulate canbe adhered to or on the surface of the fiber. The particulate can beembedded into the fiber and can be partially or fully surrounded by thefiber mass. In order to form these structures, the particulate can becombined with the fiber after spinning, can be added to the fiber duringspinning in the time the fiber dries and solidifies, or can be added tothe spinning solution before spinning such that the particulate isembedded partially or fully in the fiber.

One method of forming an active layer can be by dispersing the activeparticulate in an aqueous or non-aqueous phase containing components,either forming the active particulate into a sheet layer, or adheringthe active particulates to one or more of the components of the web orelement of the invention. Any of the active particulates of theinvention can be incorporated into either an aqueous or non-aqueousliquid phase for such purposes. In forming the non-aqueous material, anon-aqueous solvent, preferably a volatile solvent including suchmaterials as lower alcohols, ethers, low boiling hydrocarbon fractions,chloroform methylene chloride, dimethyl sulfoxide (DMSO) and others, canbe prepared by incorporating the active particulate of the material withsoluble or dispersible binding materials. Such a solution can be appliedto a fiber particulate sheet like substrate or other materials to form alayer containing the active particulates that can act in that form toabsorb/adsorb or react with materials entrained in the mobile fluidphase. Alternatively, the active particulate of the invention can bedispersed in an aqueous solution or suspension of binding materials thatcan be similarly combined with, or coated on, fiber particulate or websheet like substrates to form an active layer of active particulate.Alternatively, the active particulate of the invention can be dispersedor suspended in a mixed aqueous organic phase that combines an aqueousphase with organic phase. The organic phase can comprise additionalsolvents or other organic liquids or can comprise aqueous polymericphase such as acrylic polymers, PTFE polymers. Such mixed phases canform layers containing the active particulate and additionally cancontain cross-linking components that can form bonds between adjacentpolymers, further curing the coatings of films.

A heat treatment or thermal bonding process can be used to form adistinct layer in which there is no fully distinct fiber. The heattreatment can heat the individual fibers to a temperature at or above afusion or melting point of the individual fibers and then cause thefibers to adhere, coalesce, or form into a fused network, membrane ormembrane-like structure. Depending on the temperature and pressure andtime of the heat treatment, the heat treatment can convert the fibersfrom a randomly distributed layer of fiber of intermediate length havingonly surface contact into a layer where fibers are more intimatelyassociated. At a minimum, the fiber is heated such that at theintersections of the fibers, the fibers fuse to form a fused network.With additional heat pressure, or time of heat treatment, the fibers canfurther melt and further coalesce into a more intimately associated web.With further temperature, time, and pressure, the fiber can more fullymelt and spread into a porous membrane-like structure. The heattreatment also can alter the location of the particulate. In theinstance that the fiber is simply distributed throughout, theparticulate is distributed through the fine fiber. The heat treatmentcan fix the particulate into a structure in which the particulate issurface bonded to the heat treated fibrous, web, or membrane-likestructure; however, depending again, on the temperature, time ofheating, and pressure, the particulate can be incorporated into andthroughout the porous membrane-like structure. Such a heat treated orcalendared structure can have a layer of thickness that approximatesthat of the original fine fiber layer, or results in a layer that isthinner than the original fine fiber layer. Accordingly, if the originalfine fiber layer has a thickness that ranges from about 0.5 to 200microns, the resulting layer can have a thickness that ranges from about0.5 to about 150 microns or smaller often up to 100 microns andsometimes up to 50 microns, depending on the amount of fiber spun, theparticulate content and the degree of heat treatment, including heating,pressure, and time. One form of such a heat treatment process is thecalendaring operation that can be used thermally. The calendaringprocess uses rollers, rollers and embossers, or embossers to form theheat treated layers. An embosser can be used with a bonding pattern thatcan result in a regular, intermediate, or random pattern. When a patternis used, the pattern can occupy up to 50 percent of the surface area ormore. Typically, the bonded array occupies about 1 to 75 percent of thesurface area, often about 10-50 percent of the surface area.

Depending on the nature of the fine fiber used in the various layers andthe rate of manufacture of the composites, the calendaring processparameters such as time, temperature, and pressure can be varied toachieve acceptable results. The temperature of the calendared rollerscan range from about 25-200° C. The pressure exerted on the layers usingthe calendaring rollers or combination of rollers can range up to 500psi and the speed of the composite through the heat treatment stationcan range from about 1 to about 500 feet per minute. The operatingparameters of the heat treatment station must be adjusted such that theappropriate amount of heat is delivered to the fiber to obtain thecorrect ultimate structure. The heat cannot be so little as not tosoften or melt some portion of the fiber and cannot be such that thefiber is simply melted and dispersed into the substrate. The total heatdelivered can be readily adjusted to bond the fiber, soften the fiberoverall or fully form the fibers into a porous membrane. Such minoradjustment of the operating parameters is well within the skill of theartisan.

The web or element of the invention can be comprised of a variety ofdifferent layers. Such layers can include both active and inactivelayers. Active layers typically comprise a web of fine fiber with theparticulates dispersed within the fine fiber or other impregnated layersor layers containing adsorbent/absorbent or reactive particulate orother such structures. Such layers can be formed into the useful elementof the invention combined with protective layers, spatial layers, activelayers, inactive layers, support layers, and all can be incorporated orencapsulated into conventional cartridge panel or other such protectivestructures. A preferred form of the active particulate comprises anadsorbent carbon particulate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B shows an end view of an element of the invention inwhich the element comprises layers of active media combined with layersof inactive media to provide a flow channel to regulate efficiency andactivity.

FIG. 2 is an end view of a spiral wound media that has a chemicalfiltration media wound with a plastic mesh screen for spacing thelayers. Such a structure is a flow by structure having little or nofiltration properties but having substantial reactive adsorptive orreactive capacity.

FIG. 3 is a cross section of an assembly of the structures of theinvention. The assembly comprises a chemical filtration media and aspacer layer. The chemical filtration media comprises a nanofiber layerwith the dispersed active particulate within the nanofiber layer. Thespacer media is a layer that provides sufficient open volume within thestructure to ensure that fluid can flow with little impediment throughthe structure.

FIGS. 4A and B are graphical representation apparatus that can be usedto form the fine fiber layers of the invention by combining particledeposition with electrospinning of the fine fiber from polymer solution.

FIGS. 5 and 6 are a test apparatus and test results for the removal of atoluene test contaminant in air using a element of the invention.

FIG. 7 shows the performance of a high surface area coconut shell carbonplaced within the web of our fine fiber matrix in acceleratedbreakthrough test.

DETAILED DISCUSSION OF THE INVENTION

The particulate materials of the invention have dimensions capable ofimproving the active properties and filtration properties of the mediaand layers of the invention. The materials can be made of a variety ofuseful materials that are inert, reactive, absorptive, or adsorptive.The materials can either be substantially inert to the mobile phase andentrained particulate load passing through the web or the materials caninteract with the fluid, dissolved portions of the fluid or theparticulate loading in the fluid. Some or all of the particulate can beinert. Preferred particulates are active, reactive, absorbent, oradsorbent materials. For the purpose of this invention, the term “inert”indicates that the material in the web does not either substantiallychemically react with the fluid or particulate loading, or substantiallyphysically absorb or adsorb a portion of the fluid or the particulateloading onto the particulate in any substantial quantity. In this“inert” mode, the particulate simply alters the physical parameters ofthe fiber layer and the media including one or more fiber layers. Theactive particulate of the invention can be added to any layer of theelement of the invention using a variety of add on techniques. Theparticulate of the invention can be incorporated into the fine fiberlayer during spinning of the fiber as discussed elsewhere in theapplication. In addition, the active particulate of the invention can bedissolved or dispersed into an aqueous or nonaqueous or mixed aqueousliquid and applied to any layer of a useful element of the invention.

When using an active particulate that interacts with the fluid or theparticulate loading, the particulate can, in addition to altering thephysical properties of the media or layers, react with or absorb oradsorb a portion of either the mobile fluid or the particulate loadingfor the purpose of altering the material that passes through the web.The primary focus of the technology disclosed herein is to improve thetreatment properties of the layers to increase thereactivity/absorbent/adsorbent capacity or lifetime of the physicalstructure of the media or layers, and to improve filter performancewhere needed. In many such applications, a combination of an inertparticle and an interactive particle will then be used.

The invention relates to polymeric compositions in the form of finefiber such as microfibers, nanofibers, in the form of fiber webs, orfibrous mats used with a particulate in a unique improved filterstructure. The web of the invention comprises a substantially continuousfiber phase and dispersed in the fiber mass a fiber separation means. Inthe various aspects of the invention, the fiber separation means cancomprise a particulate phase in the web. The particulate can be found onthe surface of the web, in surface products or throughout void spacesformed within the web. The fibrous phase of the web can be formed in asubstantially singular continuous layer, can be contained in a varietyof separate definable layers or can be formed into an amorphous mass offiber having particulate inclusion phases throughout the web randomlyforming inclusion spaces around the particulate and internal websurfaces. The particulate has a major dimension of less than about 5000microns. For example, the particulate can have a major dimension of lessthan 200 microns, and can typically comprise about 0.05 to 100 micronsor comprises about 0.1 to 70 microns. In the substantially continuousfine fiber layer, the layer has a layer thickness of about 0.0001 to 1cm, 0.5 to 500 microns, about 1 to 250 microns, or about 2 to 200microns. In the layer, dispersed in the fiber, is a means comprising aparticulate with a particle size of about 0.25 to 200 microns, about 0.5to 200 microns, about 1 to 200 microns about 10 to 200, or about 25 to200 microns. The particulate is dispersed throughout the fiber in thelayer. The particulate is present in an amount of about 0.1 to 50 vol %,about 0.5 to 50 vol %, about 1 to 50 vol %, about 5 to 50 vol % or about10 to 50 vol %. The fiber has a diameter of about 0.001 to about 2microns, 0.001 to about 1 micron, 0.001 to about 0.5 micron, or 0.001 toabout 5 microns, and the layer having a fine fiber solidity of about 0.1to 65%, about 0.5 to 50%; about 1 to 50%; about 1 to 30% and about 1 to20%. The particulate is available in the layer in amount of about 1 to1000 gm-m⁻², about 5 to 200 gm-m⁻² or about 10 to 100 gm-m⁻² of thelayer.

The invention also relates to a membrane or membrane-like layer having astructure resulting from the polymeric material in the form of finefiber. The membrane is formed by heat treating the fine fiber and theparticulate to form a porous membrane. The membrane is a substantiallycontinuous membrane or film-like layer having the particulate adhered tothe surface of the membrane, imbedded into the membrane, or fullysurrounded by the membrane polymer mass. In the membrane of theinvention, the particulate can have a major dimension of less than 200microns and typically has a dimension of about 0.05 to 100 microns orabout 0.1 to 70 microns. The thickness of the membrane typically rangesfrom about 0.5 to about 5 microns having a pore size that ranges fromabout 0.1 to 5 microns often about 1 to 2 microns. The preferredmembrane has a thickness of less than about 20 microns, has a pore sizeof about 0.5 to 3 microns. The particulate is present in the membranestructure in an amount of about 0.1 to 50 vol %. Lastly, in themembrane, the particulate is available in the membrane layer in anamount of up to about 10 kg-m⁻² typically about 0.1 to 1,000 gm-m⁻²about 0.5 to 200 gm-m⁻² or about 1 to 100 gm-m⁻² of the membrane.

The particulate can take a variety of regular geometric shapes oramorphous structures. Such shapes can include amorphous or randomshapes, agglomerates, spheres, discs, ovals, extended ovals, cruciformshapes, rods, hollow rods or cylinders, bars, three dimensionalcruciform shapes having multiple particulate forms extending into space,hollow spheres, non-regular shapes, cubes, solid prisms of a variety offaces, corners and internal volumes. The aspect ratio of thenon-spherical particulate (the ratio of the least dimension of theparticle to the major or largest dimension) of the invention can rangefrom about 1:2 to about 1:10, preferably from about 1:2 to about 1:8.

The particulate of the invention can be made from both organic andinorganic materials and hybrid. The particulate that is non-interactingwith the mobile fluid or entrained particulate phase comprises organicor inorganic materials. Organic particulates can be made frompolystyrene or styrene copolymers expanded or otherwise, nylon or nyloncopolymers, polyolefin polymers including polyethylene, polypropylene,ethylene, olefin copolymers, propylene olefin copolymers, acrylicpolymers and copolymers including polymethylmethacrylate, andpolyacrylonitrile. Further, the particulate can comprise cellulosicmaterials and cellulose derivative beads. Such beads can be manufacturedfrom cellulose or from cellulose derivatives such as methyl cellulose,ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, andothers. Further, the particulates can comprise a diatomaceous earth,zeolite, talc, clay, silicate, fused silicon dioxide, glass beads,ceramic beads, metal particulates, metal oxides, etc. Particulatesintended for use in the present invention are characterized by averagesize in the range of from about 0.01 to 510 microns. Although submicronactive particles are used, the present invention is applicable to fineparticles up to 100 microns in average size. In any event, the averagesize of the active particles will be on the order of approximately 0.01to 0.0001 of the average size of the particulates. Therefore, arelatively larger average size of the active particles requires a largeraverage size of the particulate. Particles include carbon particles suchas activated carbon, ion exchange resins/beads, zeolite particles,diatomaceous earth, alumina particles such as activated alumina,polymeric particles including, for example, styrene monomer, andabsorbent particles such as commercially available superabsorbentparticles. Particularly suitable absorbent/adsorbent particles are lowdensity, porous particles, and have pores and cavities including surfacecavities, ranging in diameter from about the minimum for the pore sizein carbon is 0.00035 microns, which is the carbon-carbon distance to 100microns and interconnected by smaller pores. These pores and cavitiesbeneficially provide inner surface for deposition, in particularmonolayer deposition, of fine particles having an average size in therange of about 0.01 to 10 microns, and thereafter for accessibility tothe immobilized fine particles. 1 cm³ of these particles provides inbulk approximately 75 to 1,500 m² of available surface. Carbonparticulates can be used in the form of filing divided activated carbon.Such activated carbons can be combined with other reactive adsorbent oradsorbent species that can be blended with, or adsorbed onto, the carbonsurface. Other forms of active carbon can be used including carbonnanotubes, nanoparticles, nanowires, nanocarbon ropes or larger latticesor constructs in which the individual elements comprise a carbonnanotube. Such nanoparticles, such as buckyballs, smaller nanotubes (ornanotube portions thereof), nanoropes, etc. can be incorporated withinthe interior volume of the nanotube or incorporated into the carbon atomlattice of the nano structure. Additional atoms, molecules or componentscan add structure or function to the nano particulate material.

Small molecule, oligomeric and polymeric materials can be used in theinvention. Small molecules typically have molecular weights of less thanabout 500, are typically made up of a single identifiable molecular unitand typically the units do not repeat in the molecular structure.Oligomer structures typically have somewhat larger molecular weights buttypically have 2 to 10 repeating molecular units in a structure. Polymerunits typically have substantially higher molecular weights andtypically have substantially greater than 10 repeating units in apolymer structure. The differentiation between oligomeric and polymericstructures is not always clear cut; however, as the number of repeatunits in the structure increases, the material tends to become morepolymeric in nature.

The particulate can be mono-disperse or poly-disperse. In mono-disperseparticulate, the majority of the particles are similar in diameter orthe major dimension. For example, one example of a mono-disperseparticulate has 80% to 90% of the particulate within about 0.8±0.5microns or about 1±0.25 micron. In a poly-disperse material, theparticulate has a substantial portion of particles with differentdiameters. A poly-disperse material could be a mixture of twomono-disperse materials or a material with a substantial amount ofparticulate material present throughout a broad range (e.g.) 0.1 to 10or 0.01 to 100 microns.

The spheres or other shapes can be in a variety of different physicalforms including solid and hollow form. The particulate can have asubstantially spherical or slightly oval shaped spherical structure. Thespheres can be solid or can have a substantial internal void volume. Theshell thickness of the sphere can range from about 0.05 to about 500microns while the sphere can range from about 0.5 to about 5000 microns.Other circular structures that can be used include simple toroidalstructures, spiral or helical structures, or interlocking link typechain structures.

The particulate of the invention can also comprise a reactive absorbentor adsorbent fiber-like structure having a predetermined length anddiameter. The aspect ratio of such a fiber is typically about 1 to about10:1 having a fiber diameter that is typically larger in diameter thanthe fine fiber of the structure. The diameter ratio of the particulatefiber to the fine fiber is typically about 0.5 to about 5000:1. Avariety of other regular shapes can be used including cylindrical,hollow cylindrical, cruciform structures, three-dimensional cruciformstructures, I-beam structures, and others. The particulate can also beirregular in shape such that the particulate has a relativelywell-defined major and minor dimension but has an exterior surface thatis substantially irregular in nature. Many amorphous organic andinorganic particulates can have an irregular shape, but can have a sizethat can provide the spacing property of the particulate material.Depending upon the physical form and chemical nature of the spheres, thedimensions of the spheres can be manipulated by a secondary process suchas super absorbency, solvent swelling, heat expansion, porosity changes,etc. Microspheres available from Expancel® can be heat-treated to expandthe volume of the microspheres tremendously. Fine fiber and microspherecomposite media can be produced according to this invention, and laterupon a secondary treatment—not limited to heat—the structure of thecomposite media can be tuned in a controlled way, for example in theExpancel® case, depending upon the level of applied heat andtemperature, one can control the degree of expansion of themicrospheres. For example, by expanding the microspheres, the thicknessand loftiness of the structure can be increased and thereby filtrationproperties can be altered in a desired way. It should be understood thatsuch changes in the physical nature of the microsphere should beaccommodated by the elasticity of the fine fiber as they would stretchin the case of expansion of the microspheres. Depending upon thereversibility of the change in microspheres, one can also create loftystructures and then collapse/shrink the structure to createdense/compact filtration structures.

The web can also be used in filtration applications as a surface mediaor depth media having a continuous web of fine fiber modified by thepresence of a reactive, absorptive or adsorptive spacer or separationmeans in the form of a particulate that in combination with the fiber inthe media, provides figure of merit, filtration efficiency, filtrationpermeability, depth loading and extended useful lifetime characterizedby minimal pressure drop increase. The reactive, absorptive, oradsorptive spacer or separation means causes the fiber web to attain astructure, in which the fiber mass or web portion has reduced solidity,separated fibers or separated web portions within the structure, andincreased depth of fiber layer, without increasing the amount of polymeror the number of fibers in the web. The reactive, adsorptive orabsorptive, portion of the fiber web can react with reactive chemicalspecies within a mobile fluid passing through the fiber layer or suchchemical components of the mobile fluid can be absorbed or adsorbed bythe absorptive or adsorptive portion of the fiber layer. The activeparticulate can be used with an inert particulate as long as theactivity or activities of the particulate is maintained. The resultingstructure obtains improved filtration properties in combination withresistance to increased pressure drop, improved (Figure of Merit,)improved permeability, improved efficiency, and the ability to removeboth a particulate non-reactive load and a reactive gaseous orparticulate load from a mobile fluid stream passing through the fiberlayer. The fine fiber of the invention can be in the form of astructural fiber as discussed above. The fine fiber can be spun from areactive fiber. Such reactive fibers can be made from polymers havingreactive side chains such as amines, sulfonic acid, carboxylic acid, orother functional groups of side chains. Such side chains can be derivedfrom the polymer itself. For example, a polyamine can be formed with ahighly functional polyamine leaving acid and amine and meanfunctionality on the polymer side chains of substituents. Similarly,polysulfone or polyacrylic acid material can be formed having active orreactive acid groups. Similarly, ion exchange resin materials can bemade having, within the resin particulate, acid, strongly acid, basic,or strongly basic functional groups that can add absorbent or reactiveproperties to the invention. Such materials can be dissolved orsuspended and can be spun with the conventional fibers of the invention,or can be spun separately into the particle containing webs of theinvention.

The web can be spun in such a way to disperse the active particulate oractive separation means into the fiber. A preferred active particulateor spacer means comprises a reactive, absorptive or adsorptiveparticulate. Such particulate can be dispersed within the polymercontaining solution. The particulate can be added to the web duringformation or can be added after formation. Such a web, when electrospun,is characterized by a mass of interconnected nanofiber or fine fiberwith the active separation or spacer means or particulate dispersedwithin the fiber web on the surface of the fiber web. Within the fiberweb, the spacer particulate creates void spaces within theinterconnected fibrous structure that reduces solidity and increasesmobile fluid flow. The invention also comprises a web formed by forminga fine fiber mass with the simultaneous addition or a post spinningaddition of the spacer particulate to the fiber layer. In such anembodiment, the particulate is interspersed throughout the mass offibrous material. Lastly, the invention involves forming the spun layerin a complete finished web or thickness and then adding the activeparticulate to the surface of the web prior to incorporating the webinto a useful article. Subsequent processing including lamination,calendaring, compression or other processes can incorporate theparticulate into and through the fiber web. One advantage of eithersimultaneous addition of the particulate to the web as it is formed orto the web after formation, is obtained when the particulate is asolvent soluble particulate. Dissolving the soluble particulate in thesolution would result in the incorporation of the material into thefiber without maintaining the particulate as a separate phase in theweb. Adding the particulate to the web after formation preserves thesolvent soluble material in its particulate form.

The web of the material can also have a gradient structure. In thisdisclosure, the term “gradient” indicates that some component (density,solidity, fiber size, etc.) of the web varies from one surface of theweb to the opposite surface of the web. The gradient can becharacterized by a variation in amount of active particulate, varyingproportions of active and inert particulate, or other variation inparticulate. The gradient can also be characterized in terms of avariation in the weight or the number of fibers. The gradient is formedby forming successively more or less fibers or more or less particulateswithin the web as the web is formed. Further, the concentration ofspacer means or particulate can have a gradient aspect in which thesize, weight or number of particulate materials per volume issubstantially increased or reduced from one surface of the web to theother. The media of the invention can be used in the form of a singlefine fiber web or a series of fine fiber webs in a filter structure.

The term “fine fiber” indicates a fiber having a fiber size or diameterof 0.001 to less than 5 microns or about 0.001 to less than 2 micronsand, in some instances, 0.001 to 0.5 micron diameter. A variety ofmethods can be utilized for the manufacture of fine fiber. Chung et al.,U.S. Pat. No. 6,743,273; Kahlbaugh et al., U.S. Pat. No. 5,423,892;McLead, U.S. Pat. No. 3,878,014; Barris, U.S. Pat. No. 4,650,506;Prentice, U.S. Pat. No. 3,676,242; Lohkamp et al., U.S. Pat. No.3,841,953; and Butin et al., U.S. Pat. No. 3,849,241; all of which areincorporated by reference herein, disclose a variety of fine fibertechnologies. The fine fiber of the invention is typically electrospunonto a substrate. The substrate can be a pervious or imperviousmaterial. In filtration applications non-woven filter media can be usedas a substrate. In other applications the fiber can be spun onto animpervious layer and can be removed for down stream processing. In suchan application, the fiber can be spun onto a metal drum or foil. Thesubstrate can comprise an expanded PTFE layer or Teflon® layer. Suchlayers are useful in a variety of applications that can provide bothfiltration and activity from the active particulate.

For the purpose of this patent application, the term “adsorptive”indicates a particle that is active to adsorb and accumulate materialfrom a fluid stream on the surface of a particle. The term “absorptive”indicates that the particle has the capacity to accumulate material froma fluid stream into the interior or void space or spaces within aparticle. “Chemically reactive” indicates that the particulate has thecapacity to react with and chemically change both the character of theparticle and the chemical character of the material in the fluid stream.A “fluid stream”, in this application, indicates either a gaseous or aliquid stream that can contain a particulate. The particulate can beeither filtered from the fluid stream or the particulate can beadsorbed, absorbed or reacted with the particulate material of theinvention. The term “active particulate”, when used in this disclosure,refers to the absorptive, adsorptive or reactive particulate. The term“inert particulate” refers to a particulate that has no substantialabsorptive, adsorptive or reactive capacity. Such particles can be usedas a separation means or to occupy space.

For the purpose of this invention, the term “media” includes a structurecomprising a web comprising a substantially continuous fine fiber massand the separation or spacer materials of the invention dispersed in thefiber. In this disclosure the term “media” indicates the web of theinvention, comprising the fine fiber and dispersed particulate incombination with a substrate of some active or inert type disclosedherein. The term “element” indicates the combination of the “media” ofthe invention with another component including cartridge components inthe form of (e.g.) cylinder or flat panel structures. In thisdisclosure, the term “web” includes a substantially continuous orcontiguous fine fiber phase with spacer particulate phase. A continuousweb is necessary to impose a barrier to the passage of a particulatecontaminant loading in a mobile phase. A single web, two webs ormultiple webs can be combined to make up the filter media of theinvention.

“Figure of Merit” can be thought of as a benefit to cost ratio, whereefficiency is the benefit, and normalized pressure drop (ΔP) is the cost(ΔP/media velocity). The “cost” is normalized so that one can compareFigures of Merit from tests run at different velocities. Figure of Meritis simply an index to compare media. Larger Figure of Merit values arebetter than small. The formula for calculating Figure of Merit is:Figure of Merit=−Ln(penetration)/(ΔP/media face velocity)

In the equation presented above, ΔP is the pressure drop across themedia and the unit used in the equation is cm Hg; media face velocityhas the unit of cm/sec; Ln(penetration) is the natural logarithm ofpenetration. And penetration is defined as:Penetration=1−Efficiency

The standard units of measure which Figure of Merit is reported in aregiven below:

1/(cm Hg)/(cm/sec) or (cm/sec)/cm Hg

In many applications, especially those involving relatively high flowrates, an alternative type of filter media, sometimes generally referredto as “depth” media, is used. A typical depth media comprises arelatively thick tangle of fibrous material. Depth media is generallydefined in terms of its porosity, density or percent solids content. Forexample, a 2-3% solidity media would be a depth media mat of fibersarranged such that approximately 2-3% of the overall volume comprisesfibrous materials (solids), the remainder being air or gas space.

The fine fiber layers formed on the substrate in the filters of theinvention should be substantially uniform in particulate distribution,filtering performance and fiber distribution. By substantial uniformity,we mean that the fiber has sufficient coverage of the substrate to haveat least some measurable filtration efficiency throughout the coveredsubstrate. The media of the invention can be used in laminates withmultiple webs in a filter structure. The media of the invention includesat least one web of a fine fiber structure. The substrate upon which thefine fiber and active particulate can be formed can be either active orinactive substrate. Such substrates can have incorporated into thesubstrate layer active materials in the form of coatings, particulates,or fibers that can add adsorbent/absorbent or reactive properties to theoverall structure. The overall thickness of the fiber web is about 1 to100 times the fiber diameter or about 1 to 300 micron or about 5 to 200microns. The web can comprise about 5 to 95 wt.-% fiber and about 95 to5 wt.-% active particulate or about 30 to 75 wt.-% fiber and about 70 to25 wt.-% active particulate occupies about 0.1 to 50 vol % of the layeror about 1 to 50 vol % or 2 to 50 vol % of the layer. The overallsolidity (including the contribution of the active or inactiveparticulate) of the media is about 0.1 to about 50%, preferably about 1to about 30%. The solidity of the web without including the contributionof the particulate in the structure is about 10 to about 80%. The filtermedia of the invention can attain a filtration efficiency of about 20 toabout 99.9999% when measured according to ASTM-1215-89, with 0.78μmonodisperse polystyrene spherical particles, at 13.21 fpm (4meters/min) as described herein. When used in HEPA type application, thefilter performance is about 99.97% efficiency at 10.5 fpm and 0.3 micronNaCl or DOP particle size. Efficiency numbers in respect to this type ofefficiency testing (0.3 micron DOP at 10.5 fpm test velocity), yield anefficiency in the range of 20 to 99.9999%

M The Figure of Merit can range from 10 to 10⁵. The filtration web ofthe invention typically exhibits a Frazier permeability test that wouldexhibit a permeability of at least about 1 meters-minutes⁻¹, preferablyabout 5 to about 50 meters-minutes⁻¹ When used as a inactive particulateor separation means, the particulate that characterizes the particulatephase of the web of the invention is a particulate that is either inertto the mobile phase and the entrained contaminant load or has somedefined activity with respect to the mobile fluid or the load.

The particulate materials of the invention have dimensions capable ofimproving both the filtration properties of the media and the activereactive, absorbent or adsorbent character of the structures of theinvention. The materials can be made of a variety of useful materials.The materials can either be substantially inert to the mobile phase andentrained particulate load passing through the web or the materials caninteract with the fluid or particulate loading. In an “inert” mode, thespacer particulate simply alters the physical parameters of the fiberlayer and the media including one or more fiber layers. When using aparticulate that interacts with the fluid or the particulate loading,the particulate can, in addition to altering the physical properties ofthe media or layers, react with or absorb or adsorb a portion of eitherthe mobile fluid or the particulate loading for the purpose of alteringthe material that passes through the web. The primary focus of thetechnology disclosed herein is to improve the physical structure andabsorptive, reactive or adsorptive character of the media or layers andto improve filter performance. For that purpose, an active or an inertparticle can be used. In certain applications, a substantially inertparticle can be used in combination with a particulate that interactswith the mobile phase or particulate loading. In such applications, acombination of an inert particle and an interactive particle will beused. Such a combination of active particulate and inert particulate canprovide both improved filter property and absorption, or adsorptionproperties.

The preferred fiber separation active, adsorptive or absorptive, meanscomprises a particulate. Such a particulate, used in the unique filterstructures of the invention, occupies space within the filter layer ormat, reduces the effective density of the fiber, increases the tortuouspathways of the fluid through the filter and absorbs, adsorbs or reactswith the fluid or materials dissolved or dispersed in the fluid.Alternatively, the particulate can provide the mechanical space holdingeffect while additionally chemically reacting with the mobile fluid oradsorbing or absorbing gaseous, liquid or solid components in the mobilefluid. The active layer of the invention can comprise a nanofiber layerand dispersed within the nanofiber layer, the reactive, absorptive, oradsorptive particulate of the invention. The nanofiber layers of theinvention typically range from about 0.5 to about 300 microns, 1 toabout 250 microns or 2 to about 200 microns in thickness and containwithin the layer about 0.1 to about 50 or 10 to about 50 vol % of thelayer in the form of both inert (if any) and the active particulate ofthe invention. In this case, the active particulate of the invention canbe combined with inert spacer particulate in some amount. The activeparticulate of the invention acting to absorb, adsorb or react withcontaminants within the fluid flow while the inert particulate simplyprovides an excluded volume within the layer to reduce solidity, improveefficiency and other filtration properties.

The creation of low pressure drop active particulate, chemicallyreactive, absorptive, or adsorptive substrates for the removal of gasphase contaminants from airstreams is from flat sheet rolls ofabsorptive/adsorptive/reactive media that are layered or rolled togetherwith a spacer media to form an adsorptive/reactive substrate with openchannels and absorptive/adsorptive/reactive walls. Additionally, thespacer media can be made to be absorptive/adsorptive/reactive so as tocontribute to the overall life/performance of the final chemical unit.The spacer media that creates the open channels can be created from amesh, single lines of a polymer bead, glue dots, metal ribs, corrugatedwire/polymer/paper mesh, corrugated metal/paper/polymer sheets, stripsof polymer, strips of adhesive, strips of metal, strips of ceramic,strips of paper, or even from dimples placed in the media surface. Thesespacer media can be made absorptive/adsorptive/reactive by coating themor extruding/forming them with/from absorptive/adsorptive/reactivematerials. The contaminated airflow is primarily directed along thechannel created by the spacer media. This air comes into contact withthe adsorptive/reactive media walls and/or spacer media and subsequentlybecomes adsorbed or reacted. The channel size and shape is controlled bythe shape and size of the space media. Examples include squares,rectangles, triangles, and obscure shapes that may be created by adotted pattern of polymer/adhesive. The chemistry of the walls andspacer media can be made specific to adsorb acidic, basic, and organicand water vapors, as well as several specific classes of compoundsincluding reactive carbonyl compounds, including formaldehyde,acetaldehyde and acetone.

The reactive material can begin in many forms or functions. These formsinclude layers of reactive particles attached to a substrate. Thereactive materials can be held together with adhesive or fibers toencapsulate, or simply hold, the particles and/or additional scrimmaterials are attached to hold the reactive material in place andminimize shedding of particles. The reactive material can also besandwiched between layers of scrim. The scrim could help to produce thechannels or space between the layers. This could be accomplished with ahigh loft scrim material that would give the proper spacing as well asability to hold all the reactive particles in the media. The reactive oradsorptive particles can be held together or interspersed with fibers.The combination of particles and fibers (also nanofibers) results in amaterial that offers several advantages: increased diffusion; allowingfor the use of smaller particles, thereby increasing the externalsurface area and hence the reaction rate; increased permeation into thereactive layer; the combination of particle and chemical filtration intoa single layer; and the direct application of reactants to a filtrationapplication without the need of a substrate or carrier (i.e. impregnatedadsorbent).

Besides using particles that have been impregnated or coated withreactive species, it is obvious to anyone skilled in the art that thesemodifications can be performed after forming the fibrous web andstructures. Imparting reactive activity to the particles and web afterforming the fibrous web and structure can be accomplished using manydifferent coating processes. For example, spray coating, dip coating,aerosol deposition, chemical vapor deposition, Kiss coating, and vacuumcoating. A final step may involve a drying process that may, or may not,include thermal treatments, gas purging, or vacuum methods.

Specific Aspects:

A first aspect of the invention involves the use of a rolled substrateof an active particulate such as an activated carbon from KX Industries(trade name PLEXX) rolled with a nylon mesh to create a low pressuredrop volatile organic chemical filter. Similar activated carbonsubstrates in flat sheets, or rolled good forms are available from othersuppliers and can be applied in a similar manner. The material needs tobe able to maintain the shape and flexibility to be able to form thevarious filter elements and minimize the shedding of particles. Anotheraspect of the invention involves the use of nanofibers and an activeparticulate such as an activated carbon powder co-dispersed into an airstream, or chamber, and deposited onto a substrate that can be any thin,flexible, porous substrate (e.g. a scrim, paper, mesh, etc.). Thenanofibers entrap, or hold, the adsorptive particles in a thin layerand, as such, minimize the shedding of particles. This entirecombination of substrate layer and nanofiber/adsorbent layer is thenrolled with a spacer layer that provides non-restrictive channels forair flow or transport. The layer can comprise a mix of particulates thateach react with a different chemical species. For example, activatedcarbon may also contain an impregnant that is specific for acidic,basic, or reactive organic contaminants. Examples include, citric acidfor the removal of amines and ammonia, potassium hydroxide for theremoval of sulfur dioxide and other acid gases, and2,4-dinitrophenylhydrazine for the removal of carbonyl containingcompounds. A third aspect of the invention is the use of nanofibers andcitric acid powder, or granules, co-dispersed into an air stream, orchamber, and deposited onto a substrate that can be any thin, flexible,porous substrate (e.g. a scrim, paper, mesh, etc.).

Still another aspect of the invention involves the use of catalytic TiO₂particles, fibers, or layers, in the element of the invention. Suchcatalytic layers, when irradiated with UV light, can cause a chemicalreaction between the catalyst and materials entrapped in the mobilephase, and can remove the materials or change them from a noxious orharmful material into a benign material. Ambient light with someproportion of UV (less than 350 nm) and visible radiation (about 350 to700 nm) can often be the source of sufficient radiation energy to obtainthe catalytic effect for the TiO₂ in the element. If ambient conditionsare insufficient for activity the element can be used with a separate UVsource. Fluorescent UV sources are known and can be used either as aseparate irradiating source, or can be incorporated into the element toprovide substantial amount of UV radiation onto the TiO₂.

The nanofiber entraps, or holds the reactive particles in a thin layer,and as such, minimizes the shedding of particles. This entirecombination of substrate layer and nanofiber/adsorbent layer is thenrolled with a spacer layer that provides non-restrictive channels forair flow or transport. The fine fiber layer that contains the activeparticulate dispersed within the layer can be made from a variety ofpolymeric species. Since polymer species include a vast array of polymermaterials. The polymer can be a single polymer species or blend ofpolymeric species or a polymer alloy of two or more polymer species. Thefibers can be made using any known fine fiber manufacturing techniquethat involves combining polymers, if necessary with other polymers oradditives, and then using a forming technique to shape the polymer intothe fine fiber polymer desired. A 48%-52 wt % blend ratio between thepolymer in example 1 and the polymer in example 2 respectively was used.

A further aspect of the invention is the use of nanofibers andion-exchange resins, or granules co-dispersed into an air stream, orchamber, and deposited onto a substrate that can be any thin, flexible,porous substrate (e.g. a scrim, paper, mesh, etc.). The nanofibersentrap, or hold, the reactive particles in a thin layer and, as such,minimize the shedding of particles. This entire combination of substratelayer and nanofiber/adsorbent layer is then rolled with a spacer layerthat provides non-restrictive channels for air flow or transport.

Polymer materials that can be used as the fiber polymer compositions ofthe invention include both addition polymer and condensation polymermaterials such as polyolefin, polyacetal, polyamide, polyester,cellulose ether and ester, polyalkylene sulfide, polyarylene oxide,polysulfone, modified polysulfone polymers and mixtures thereof.Preferred materials that fall within these generic classes includepolyethylene, polypropylene, poly(vinylchloride), polymethylmethacrylate(and other acrylic resins), polystyrene, and copolymers thereof(including ABA type block copolymers), poly(vinylidene fluoride),poly(vinylidene chloride), polyvinylalcohol in various degrees ofhydrolysis (80% to 99.5%) in crosslinked and non-crosslinked forms.Preferred addition polymers tend to be glassy (a Tg greater than roomtemperature). This is the case for polyvinylchloride andpolymethylmethacrylate, polystyrene polymer compositions or alloys orlow in crystallinity for polyvinylidene fluoride and polyvinylalcoholmaterials. One class of polyamide condensation polymers are nylonmaterials. The term “nylon” is a generic name for all long chainsynthetic polyamides. Typically, nylon nomenclature includes a series ofnumbers such as in nylon-6,6 which indicates that the starting materialsare a C₆ diamine and a C₆ diacid (the first digit indicating a C₆diamine and the second digit indicating a C₆ dicarboxylic acidcompound). Nylon can be made by the polycondensation of ε-caprolactam inthe presence of a small amount of water. This reaction forms a nylon-6(made from a cyclic lactam—also known as ε-aminocaproic acid) that is alinear polyamide. Further, nylon copolymers are also contemplated.Copolymers can be made by combining various diamine compounds, variousdiacid compounds and various cyclic lactam structures in a reactionmixture and then forming the nylon with randomly positioned monomericmaterials in a polyamide structure. For example, a nylon 6,6-6,10material is a nylon manufactured from hexamethylene diamine and a C₆ anda C₁₀ blend of diacids. A nylon 6,6-6,6,10 is a nylon manufactured bycopolymerization of ε-aminocaproic acid, hexamethylene diamine and ablend of a C₆ and a C₁₀ diacid material.

Block copolymers are also useful in the process of this invention. Withsuch copolymers the choice of solvent swelling agent is important. Theselected solvent is such that both blocks were soluble in the solvent.One example is a ABA (styrene-EP-styrene) or AB (styrene-EP) polymer inmethylene chloride solvent. If one component is not soluble in thesolvent, it will form a gel. Examples of such block copolymers areKraton® type of styrene-b-butadiene and styrene-b-hydrogenatedbutadiene(ethylene propylene), Pebax® type of E-caprolactam-b-ethyleneoxide, Sympatex® polyester-b-ethylene oxide and polyurethanes ofethylene oxide and isocyanates.

Addition polymers like polyvinylidene fluoride, syndiotacticpolystyrene, copolymer of vinylidene fluoride and hexafluoropropylene,polyvinyl alcohol, polyvinyl acetate, amorphous addition polymers, suchas poly(acrylonitrile) and its copolymers with acrylic acid andmethacrylates, polystyrene, poly(vinyl chloride) and its variouscopolymers, poly(methyl methacrylate) and its various copolymers, can besolution spun with relative ease because they are soluble at lowpressures and temperatures. However, highly crystalline polymer likepolyethylene and polypropylene require high temperature, high pressuresolvent if they are to be solution spun. Therefore, solution spinning ofthe polyethylene and polypropylene is very difficult. Electrostaticsolution spinning is one method of making nanofibers and microfiber.

The polyurethane (PU) polyether used in this layer of invention can bean aliphatic or aromatic polyurethane depending on the isocyanate usedand can be a polyether polyurethane or a polyester polyurethane. Apolyether urethane having good physical properties can be prepared bymelt polymerization of a hydroxyl-terminated polyether or polyesterintermediate and a chain extender with an aliphatic or aromatic (MDI)diisocyanate. The hydroxyl-terminated polyether has alkylene oxiderepeat units containing from 2 to 10 carbon atoms and has a weightaverage molecular weight of at least 1000. The chain extender is asubstantially non-branched glycol having 2 to 20 carbon atoms. Theamount of the chain extender is from 0.5 to less than 2 mole per mole ofhydroxyl terminated polyether. It is preferred that the polyetherpolyurethane is thermoplastic and has a melting point of about 140° C.to 250° C. or greater (e.g., 150° C. to 250° C.) with 180° C. or greaterbeing preferred.

In a first mode, the polyurethane polymer of the invention can be madesimply by combining a di-, tri- or higher functionality aromatic oraliphatic isocyanate compound with a polyol compound that can compriseeither a polyester polyol or a polyether polyol. The reaction betweenthe active hydrogen atoms in the polyol with the isocyanate groups formsthe addition polyurethane polymer material in a straight forwardfashion. The OH:NCO ratio is typically about 1:1 leaving little or nounreacted isocyanate in the finished polymer. In any unreactedisocyanate compound, reactivity can be scavenged using isocyanatereactive compounds. In a second mode, the polyurethane polymer can besynthesized in a stepwise fashion from isocyanate terminated prepolymermaterials. The polyurethane can be made from an isocyanate-terminatedpolyether or polyester. An isocyanate-capped polyol prepolymer can bechain-extended with an aromatic or aliphatic dihydroxy compound. Theterm “isocyanate-terminated polyether or polyurethane” refers generallyto a prepolymer which comprises a polyol that has been reacted with adiisocyanate compound (i.e., a compound containing at least twoisocyanate (—NCO) groups). In preferred form, the prepolymer has afunctionality of 2.0 or greater, an average molecular weight of about250 to 10,000 or 600-5000, and is prepared so as to containsubstantially no unreacted monomeric isocyanate compound. The term“unreacted isocyanate compound” refers to free monomeric aliphatic oraromatic isocyanate-containing compound, i.e., diisocyanate compoundwhich is employed as a starting material in connection with thepreparation of the prepolymer and which remains unreacted in theprepolymer composition.

The term “polyol” as used herein, generally refers to a polymericcompound having more than one hydroxy (—OH) group, preferably analiphatic polymeric (polyether or polyester) compound which isterminated at each end with a hydroxy group. The chain-lengtheningagents are difunctional and/or trifunctional compounds having molecularweights of from 62 to 500 preferably aliphatic diols having from 2 to 14carbon atoms, such as, for example, ethanediol, 1,6-hexanediol,diethylene glycol, dipropylene glycol and, especially, 1,4-butanediol.Also suitable, however, are diesters of terephthalic acid with glycolshaving from 2 to 4 carbon atoms, such as, for example, terephthalic acidbis-ethylene glycol or 1,4-butanediol, hydroxy alkylene ethers ofhydroquinone, such as, for example, 1,4-di(B-hydroxyethyl)-hydroquinone,(cyclo)aliphatic diamines, such as, for example, isophorone-diamine,ethylenediamine, 1,2-, 1,3-propylene-diamine,N-methyl-1,3-propylene-diamine, N,N′-dimethyl-ethylene-diamine, andaromatic diamines, such as, for example, 2,4- and2,6-toluoylene-diamine, 3,5-diethyl-2,4- and/or -2,6-toluoylene-diamine,and primary ortho- di-, tri- and/or tetraalkyl-substituted4,4′-diaminodiphenyl-methanes. It is also possible to use mixtures ofthe above-mentioned chain-lengthening agents. Preferred polyols arepolyesters, polyethers, polycarbonates or a mixture thereof. A widevariety of polyol compounds is available for use in the preparation ofthe prepolymer. In preferred embodiments, the polyol may comprise apolymeric diol including, for example, polyether diols and polyesterdiols and mixtures or copolymers thereof. Preferred polymeric diols arepolyether diols, with polyalkylene ether diols being more preferred.Exemplary polyalkylene polyether diols include, for example,polyethylene ether glycol, polypropylene ether glycol,polytetramethylene ether glycol (PTMEG) and polyhexamethylene etherglycol and mixtures or copolymers thereof. Preferred among thesepolyalkylene ether diols is PTMEG. Preferred among the polyester diolsare, for example, polybutylene adipate glycol and polyethylene adipateglycol and mixtures or copolymers thereof. Other polyether polyols maybe prepared by reacting one or more alkylene oxides having from 2 to 4carbon atoms in the alkylene radical with a starter molecule containingtwo active hydrogen atoms bonded therein. The following may be mentionedas examples of alkylene oxides: ethylene oxide, 1,2-propylene oxide,epichlorohydrin and 1,2- and 2,3-butylene oxide. Preference is given tothe use of ethylene oxide, propylene oxide and mixtures of 1,2-propyleneoxide and ethylene oxide. The alkylene oxides may be used individually,alternately in succession, or in the form of mixtures. Starter moleculesinclude, for example: water, amino alcohols, such asN-alkyldiethanolamines, for example N-methyl-diethanolamine, and diols,such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol and1,6-hexanediol. It is also possible to use mixtures of startermolecules. Suitable polyether polyols are also thehydroxyl-group-containing polymerization products of tetrahydrofuran.Suitable polyester polyols may be prepared, for example, fromdicarboxylic acids having from 2 to 12 carbon atoms, preferably from 4to 6 carbon atoms, and polyhydric alcohols. Suitable dicarboxylic acidsinclude, for example: aliphatic dicarboxylic acids, such as succinicacid, glutaric acid, adipic acid, suberic acid, azelaic acid and sebacicacid, and aromatic dicarboxylic acids, such as phthalic acid,isophthalic acid and terephthalic acid. The dicarboxylic acids may beused individually or in the form of mixtures, for example in the form ofa succinic, glutaric and adipic acid mixture. It may be advantageous forthe preparation of the polyester polyols to use, instead of thedicarboxylic acids, the corresponding dicarboxylic acid derivatives,such as carboxylic acid diesters having from 1 to 4 carbon atoms in thealcohol radical, carboxylic acid anhydrides or carboxylic acidchlorides. Examples of polyhydric alcohols are glycols having from 2 to10, preferably from 2 to 6, carbon atoms, such as ethylene glycol,diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,10-decanediol, 2,2-dimethyl-1,3-propanediol, 1,3-propanediol anddipropylene glycol. According to the desired properties, the polyhydricalcohols may be used alone or, optionally, in admixture with oneanother. Also suitable are esters of carbonic acid with the mentioneddiols, especially those having from 4 to 6 carbon atoms, such as1,4-butanediol and/or 1,6-hexanediol, condensation products of(omega-hydroxycarboxylic acids, for example (omega-hydroxycaproic acid,and preferably polymerization products of lactones, for exampleoptionally substituted (ε-caprolactones. These are preferably used aspolyester polyols ethanediol polyadipate, 1,4-butanediol polyadipate,ethanediol-1,4-butanediol polyadipate, 1,6-hexanediol neopentyl glycolpolyadipate, 1,6-hexanediol-1,4-butanediol polyadipate andpolycaprolactones. The polyester polyols have molecular weights of from600 to 5000.

The number of average molecular weight of the polyols from which thepolymer or prepolymers may be derived may range from about 800 to about3500 and all combinations and subcombinations of ranges therein. Morepreferably, the number of average molecular weights of the polyol mayrange from about 1500 to about 2500, with number average molecularweights of about 2000 being even more preferred.

The polyol in the prepolymers can be capped with an isocyanate compoundor can be fully reacted to the thermoplastic polyurethane (TPU). A widevariety of diisocyanate compounds is available for use in thepreparation of the prepolymers of the present invention. Generallyspeaking, the diisocyanate compound may be aromatic or aliphatic, witharomatic diisocyanate compounds being preferred. Included among thesuitable organic diisocyanates are, for example, aliphatic,cycloaliphatic, araliphatic, heterocyclic and aromatic diisocyanates, asare described, for example, in Justus Liebigs Annalen der Chemie, 562,pages 75 to 136. Examples of suitable aromatic diisocyanate compoundsinclude diphenylmethane diisocyanate, xylene diisocyanate, toluenediisocyanate, phenylene diisocyanate, and naphthalene diisocyanate andmixtures thereof. Examples of suitable aliphatic diisocyanate compoundsinclude dicyclohexylmethane diisocyanate and hexamethylene diisocyanateand mixtures thereof. Preferred among the diisocyanate compounds is MDIdue, at least in part, to its general commercial availability and highdegree of safety, as well as its generally desirable reactivity withchain extenders (discussed more fully hereinafter). Other diisocyanatecompounds, in addition to those exemplified above, would be readilyapparent to one of ordinary skill in the art, once armed with thepresent disclosure. The following may be mentioned as specific examples:aliphatic diisocyanates, such as hexamethylene diisocyanate,cycloaliphatic diisocyanates, such as isophorone diisocyanate,1,4-cyclohexane diisocyanate, 1-methyl-2,4- and -2,6-cyclohexanediisocyanate and the corresponding isomeric mixtures, 4,4′-, 2,4′- and2,2′-dicyclohexylmethane diisocyanate and the corresponding isomericmixtures, and, preferably, aromatic diisocyanates, such as2,4-toluoylene diisocyanate, mixtures of 2,4- and 2,6-toluoylenediisocyanate, 4,4′-, 2,4′- and 2,2′-diphenylmethane diisocyanate,mixtures of 2,4′- and 4,4′-diphenylmethane diisocyanate,urethane-modified liquid 4,4′- and/or 2,4′-diphenylmethanediisocyanates, 4,4′-diisocyanatodiphenylethane-(1,2) and 1,5-naphthylenediisocyanate. Preference is given to the use of 1,6-hexamethylenediisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate,diphenylmethane diisocyanate isomeric mixtures having a4,4′-diphenylmethane diisocyanate content of greater than 96 wt. %, andespecially 4,4′-diphenylmethane diisocyanate and 1,5-naphthylenediisocyanate.

For the preparation of the TPUs, the chain-extension components arereacted, optionally in the presence of catalysts, auxiliary substancesand/or additives, in such amounts that the equivalence ratio of NCOgroups to the sum of all the NCO-reactive groups, especially of the OHgroups of the low molecular weight diols/triols and polyols, is from0.9:1.0 to 1.2:1.0, preferably from 0.95:1.0 to 1.10:1.0. Suitablecatalysts, which in particular accelerate the reaction between the NCOgroups of the diisocyanates and the hydroxyl groups of the diolcomponents, are the conventional tertiary amines known in the prior art,such as, for example, triethylamine, dimethylcyclohexylamine,N-methylmorpholine, N,N′-dimethyl-piperazine,2-(dimethylaminoethoxy)-ethanol, diazabicyclo-(2,2,2)-octane and thelike, as well as, especially, organometallic compounds such as titanicacid esters, iron compounds, tin compounds, for example tin diacetate,tin dioctate, tin dilaurate or the tindialkyl salts of aliphaticcarboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate orthe like. The catalysts are usually used in amounts of from 0.0005 to0.1 part per 100 parts of polyhydroxy compound. In addition tocatalysts, auxiliary substances and/or additives may also beincorporated into the chain-extension components. Examples which may bementioned are lubricants, antiblocking agents, inhibitors, stabilizersagainst hydrolysis, light, heat and discoloration, flameproofing agents,colorings, pigments, inorganic and/or organic fillers and reinforcingagents. Reinforcing agents are especially fibrous reinforcing materialssuch as, for example, inorganic fibers, which are prepared according tothe prior art and may also be provided with a size.

Further additional components that may be incorporated into the PU arethermoplastics, for example polycarbonates andacrylonitrile-butadiene-styrene terpolymers, especially ABS. Otherelastomers, such as, for example, rubber, ethylene-vinyl acetatepolymers, styrene-butadiene copolymers and other PUs, may likewise beused. Also suitable for incorporation are commercially availableplasticisers such as, for example, phosphates, phthalates, adipates,sebacates. The PUs according to the invention are produced continuously.Either the known band process or the extruder process may be used. Thecomponents may be metered simultaneously, i.e. one shot, or insuccession, i.e. by a prepolymer process. In that case, the prepolymermay be introduced either batchwise or continuously in the first part ofthe extruder, or it may be prepared in a separate prepolymer apparatusarranged upstream. The extruder process is preferably used, optionallyin conjunction with a prepolymer reactor.

Fiber can be made by conventional methods and can be made by meltspinning the polyurethane PU or a mixed polyether urethane and theadditive. Melt spinning is a well known process in which a polymer ismelted by extrusion, passed through a spinning nozzle into air,solidified by cooling, and collected by winding the fibers on acollection device. Typically the fibers are melt-spun at a polymertemperature of about 150° C. to about 300° C.

Polymeric materials have been fabricated in non-woven and woven fabrics,fibers and microfibers. The polymeric material provides the physicalproperties required for product stability. These materials should notchange significantly in dimension, suffer reduced molecular weight,become less flexible or subject to stress cracking, or physicallydeteriorate in the presence of sunlight, humidity, high temperatures orother negative environmental effects. The invention relates to animproved polymeric material that can maintain physical properties in theface of incident electromagnetic radiation such as environmental light,heat, humidity and other physical challenges.

We have also found a substantial advantage to forming polymericcompositions comprising two or more polymeric materials in polymeradmixture, alloy format, or in a crosslinked chemically bondedstructure. We believe such polymer compositions improve physicalproperties by changing polymer attributes such as improving polymerchain flexibility or chain mobility, increasing overall molecular weightand providing reinforcement through the formation of networks ofpolymeric materials.

In one embodiment of this concept, two related or unrelated polymermaterials can be blended for beneficial properties. For example, a highmolecular weight polyvinylchloride can be blended with a low molecularweight polyvinylchloride. Similarly, a high molecular weight nylonmaterial can be blended with a low molecular weight nylon material.Further, differing species of a general polymeric genus can be blended.For example, a high molecular weight styrene material can be blendedwith a low molecular weight, high impact polystyrene. A nylon-6 materialcan be blended with a nylon copolymer such as a nylon-6,6-6,6,10copolymer. Further, a polyvinylalcohol having a low degree of hydrolysissuch as an 80-87% hydrolyzed polyvinylalcohol can be blended with afully or superhydrolyzed polyvinylalcohol having a degree of hydrolysisbetween 98 and 99.9% and higher. All of these materials in admixture canbe crosslinked using appropriate crosslinking mechanisms. Nylons can becrosslinked using crosslinking agents that are reactive with thenitrogen atom in the amide linkage. Polyvinylalcohol materials can becrosslinked using hydroxyl reactive materials such as monoaldehydes,such as formaldehyde, ureas, melamine-formaldehyde resin and itsanalogues, boric acids and other inorganic compounds. dialdehydes,diacids, urethanes, epoxies and other known crosslinking agents.Crosslinking technology is a well known and understood phenomenon inwhich a crosslinking reagent reacts and forms covalent bonds betweenpolymer chains to substantially improve molecular weight, chemicalresistance, overall strength and resistance to mechanical degradation.

We have found that additive materials can significantly improve theproperties of the polymer materials in the form of a fine fiber. Theresistance to the effects of heat, humidity, impact, mechanical stressand other negative environmental effect can be substantially improved bythe presence of additive materials. We have found that while processingthe microfiber materials of the invention, the additive materials canimprove the oleophobic character, the hydrophobic character, and canappear to aid in improving the chemical stability of the materials. Webelieve that the fine fibers of the invention in the form of amicrofiber are improved by the presence of these oleophobic andhydrophobic additives as these additives form a protective layercoating, ablative surface or penetrate the surface to some depth toimprove the nature of the polymeric material. We believe the importantcharacteristics of these materials are the presence of a stronglyhydrophobic group that can preferably also have oleophobic character.Strongly hydrophobic groups include fluorocarbon groups, hydrophobichydrocarbon surfactants or blocks and substantially hydrocarbonoligomeric compositions. These materials are manufactured incompositions that have a portion of the molecule that tends to becompatible with the polymer material affording typically a physical bondor association with the polymer while the strongly hydrophobic oroleophobic group, as a result of the association of the additive withthe polymer, forms a protective surface layer that resides on thesurface or becomes alloyed with or mixed with the polymer surfacelayers. For 0.2-micron fiber with 10% additive level, the surfacethickness is calculated to be around 50 Å, if the additive has migratedtoward the surface. Migration is believed to occur due to theincompatible nature of the oleophobic or hydrophobic groups in the bulkmaterial. A 50 Å thickness appears to be reasonable thickness forprotective coating. For 0.05-micron diameter fiber, 50 Å thicknesscorresponds to 20% mass. For 2 microns thickness fiber, 50 Å thicknesscorresponds to 2% mass. Preferably the additive materials are used at anamount of about 2 to 25 wt. %. Oligomeric additives that can be used incombination with the polymer materials of the invention includeoligomers having a molecular weight of about 500 to about 5000,preferably about 500 to about 3000 including fluoro-chemicals, nonionicsurfactants and low molecular weight resins or oligomers. Examples ofuseful phenolic additive materials include Enzo-BPA, Enzo-BPA/phenol,Enzo-TBP, Enzo-COP and other related phenolics were obtained fromEnzymol International Inc., Columbus, Ohio.

An extremely wide variety of fibrous filter media exist for differentapplications. The durable nanofibers and microfibers described in thisinvention can be added to any of the media. The fibers described in thisinvention can also be used to substitute for fiber components of theseexisting media giving the significant advantage of improved performance(improved efficiency and/or reduced pressure drop) due to their smalldiameter, while exhibiting greater durability.

Polymer nanofibers and microfibers are known; however, their use hasbeen very limited due to their fragility to mechanical stresses, andtheir susceptibility to chemical degradation due to their very highsurface area to volume ratio. The fibers described in this inventionaddress these limitations and will therefore be usable in a very widevariety of filtration, textile, membrane, and other diverseapplications.

A media construction according to the present invention includes a firstlayer of permeable coarse fibrous media or substrate having a firstsurface. A first layer of fine fiber media is secured to the firstsurface of the first layer of permeable coarse fibrous media. Preferablythe first layer of permeable coarse fibrous material comprises fibershaving an average diameter of at least 10 microns, typically andpreferably about 12 (or 14) to 30 microns. Also preferably the firstlayer of permeable coarse fibrous material comprises a media having abasis weight of no greater than about 200 grams/meter², preferably about0.50 to 150 g/m², and most preferably at least 8 g/m². Preferably thefirst layer of permeable coarse fibrous media is at least 0.0005 inch(12 microns) thick, and typically and preferably is about 0.001 to 0.030inch (25-800 microns) thick. The element of the invention, including thefine fiber and dispersed particulate layer can be combined with avariety of other layers as discussed elsewhere in the specification. Thelayers can be made as a flat or coplanar sheet version of the layers ofthe invention or can be pleated, corrugated or formed into virtually anyother cross-sectional shape needed to form the low pressure drop flowthrough element of the invention. The substrate can comprise an expandedpoly PTFE layer or Teflon layer. The substrate can also be substantiallyfree of a Teflon, an expanded poly PTFE layer, or stretched PTFE fiberor layer. Such layers are useful in a variety of in use applicationsthat can provide both filtration and activity from the activeparticulate. Such layers can also aid in confining the particulate intothe element.

In preferred arrangements, the first layer of permeable coarse fibrousmaterial comprises a material which, if evaluated separately from aremainder of the construction by the Frazier permeability test, wouldexhibit a permeability of at least 1 meter(s)/min, and typically andpreferably about 2-900 meters/min. Herein when reference is made toefficiency, unless otherwise specified, reference is made to efficiencywhen measured according to ASTM-1215-89, with 0.78μ monodispersepolystyrene spherical particles, at 20 fpm (6.1 meters/min) as describedherein.

Preferably the layer of fine fiber material secured to the first surfaceof the layer of permeable coarse fibrous media is a layer of nano- andmicrofiber media wherein the fibers have average fiber diameters of nogreater than about 2 microns, generally and preferably no greater thanabout 1 micron, and typically and preferably have fiber diameterssmaller than 0.5 micron and within the range of about 0.05 to 0.5micron. Also, preferably the first layer of fine fiber material securedto the first surface of the first layer of permeable coarse fibrousmaterial has an overall thickness that is no greater than about 30microns, more preferably no more than 20 microns, most preferably nogreater than about 10 microns, and typically and preferably that iswithin a thickness of about 1-8 times (and more preferably no more than5 times) the fine fiber average diameter of the layer.

The electrostatic spinning process can form the microfiber or nanofiberof the unit. A suitable apparatus for forming the fiber is illustratedin Barris U.S. Pat. No. 4,650,506. This apparatus includes a reservoirin which the fine fiber forming polymer solution is contained, a pumpand a rotary type emitting device or emitter to which the polymericsolution is pumped. The emitter generally consists of a rotating union,a rotating portion including a plurality of offset holes and a shaftconnecting the forward facing portion and the rotating union. Therotating union provides for introduction of the polymer solution to theforward facing portion through the hollow shaft. Alternatively, therotating portion can be immersed into a reservoir of polymer fed byreservoir and pump. The rotating portion then obtains polymer solutionfrom the reservoir and as it rotates in the electrostatic field, theelectrostatic field aligned toward the collecting media accelerates adroplet of the solution as discussed below.

Facing the emitter, but spaced apart therefrom, is a substantiallyplanar grid 60 upon which the collecting media (i.e. substrate orcombined substrate is positioned. Air can be drawn through the grid. Thecollecting media is passed around rollers which are positioned adjacentopposite ends of grid. A high voltage electrostatic potential ismaintained between emitter and grid by means of a suitable electrostaticvoltage source and connections and which connect respectively to thegrid and emitter.

In use, the polymer solution is pumped to the rotating union orreservoir from reservoir. The forward facing portion rotates whileliquid exits from holes, or is picked up from a reservoir, and movesfrom the outer edge of the emitter toward collecting media positioned onthe grid. Specifically, the electrostatic potential between grid and theemitter imparts a charge to the material that cause liquid to be emittedthere from as thin fibers which are drawn toward grid where they arriveand are collected on substrate or an efficiency layer. In the case ofthe polymer in solution, solvent is evaporated from the fibers duringtheir flight to the grid; therefore, the fibers arrive at the substrateor efficiency layer without substantial solvent. The fine fibers bond tothe substrate fibers first encountered at the grid. Electrostatic fieldstrength is selected to ensure that as the polymer material it isaccelerated from the emitter to the collecting media, the accelerationis sufficient to render the material into a very thin microfiber ornanofiber structure. Increasing or slowing the advance rate of thecollecting media can deposit more or less emitted fibers on the formingmedia, thereby allowing control of the thickness of each layer depositedthereon. The rotating portion can have a variety of beneficialpositions. The rotating portion can be placed in a plane of rotationsuch that the plane is perpendicular to the surface of the collectingmedia or positioned at any arbitrary angle. The rotating media can bepositioned parallel to or slightly offset from parallel orientation.

A sheet-like substrate is unwound at a station. The sheet-like substrateis then directed to a splicing station wherein multiple lengths of thesubstrate can be spliced for continuous operation. The continuous lengthof sheet-like substrate is directed to a fine fiber technology stationcomprising the spinning technology discussed above, wherein a spinningdevice forms the fine fiber and lays the fine fiber in a filtering layeron the sheet-like substrate. After the fine fiber layer is formed on thesheet-like substrate in the formation zone, the fine fiber layer andsubstrate are directed to a heat treatment station for appropriateprocessing. The sheet-like substrate and fine fiber layer is then testedin an efficiency monitor and nipped if necessary at a nip station. Thesheet-like substrate and fiber layer is then steered to the appropriatewinding station to be wound onto the appropriate spindle for furtherprocessing.

The element of the invention when used in a filtration mode should havea minimal pressure drop for acceptable function as a filter and toobtain the activity of the active particle(s). Such pressure dropinformation is known for the types of filtration devices of theinvention. Such pressure drop parameters define the useful life of thefiltration element of the invention. The element of the invention, whenused in a flow through mode with no intervening filter layer, shouldprovide little or no resistance to the flow of the mobile fluid throughthe element (e.g.; less 0.1 inches or less than 1-5 inches of water).Flow should not be constrained but the residence time, however, of thefluid within the element must be sufficient to obtain sufficient contactand absorbance/absorbance/reaction needed in the element to obtain thedesired activity form the active particulate within the element. Auseful residence time, depending on active particulate can be from about0.01 to as long as it is necessary to obtain some removal of entrainedmaterials. The residence time can be 0.02 second to as much as 5 minutesand typically ranges from about 0.01 to 60 seconds 0.01 to 1 second oras little as 0.02 to 0.5 second. The lifetime of such a unit is definedby the load of active particulate and the residual amount of activity inthe unit. Some small amount of pressure drop can be designed into theelement to slow the flow and extend residence time without substantiallyimpeding flow.

The media, web, layers or elements of the invention can be regenerated.In the case of a reactive particulate in the invention, the particulatecan be regenerated by chemically treating the particulate. In the caseof absorptive or adsorptive particulate, the particulate can begenerated by heating the element to a temperature sufficient to drivethe absorbed or adsorbed material from the particulate surface orinternal structure. The element can also be evacuated such that theeffects of reduced pressure can remove the volatile material from thesurface of the adsorptive particle or from the interior of theabsorptive particle.

The reactive species can be regenerated by first removing any reactionbyproducts from the reaction from the active species with the enteringmaterial in the fluid phase. In one such reaction, byproducts areremoved, the particulate remaining within the element enhanced bypassing a solution or suspension of the active material through theelement, causing the interior structure including the fine fiber layerto accumulate additional amounts of reactive material.

EXEMPLARY SECTION Example 1

A thermoplastic aliphatic polyurethane compound manufactured by Noveon®,TECOPHILIC SP-80A-150 TPU was used. The polymer is a polyetherpolyurethane made by reacting dicyclohexylmethane 4,4′-diisocyanate witha polyol.

Polymer Example 2

A copolymer of nylon 6,6,6-6,10 nylon copolymer resin (SVP-651) wasanalyzed for molecular weight by the end group titration. (J. E. Walzand G. B. Taylor, determination of the molecular weight of nylon, Anal.Chem. Vol. 19, Number 7, pp 448-450 (1947). The number of averagemolecular weight was between 21,500 and 24,800. The composition wasestimated by the phase diagram of melt temperature of three componentnylon, nylon 6 about 45%, nylon 66 about 20% and nylon 610 about 25%.(Page 286, Nylon Plastics Handbook, Melvin Kohan ed. Hanser Publisher,New York (1995)). Reported physical properties of SVP 651 resin are:

Property ASTM Method Units Typical Value Specific Gravity D-792 —  1.08Water Absorption D-570 %  2.5 (24 hr immersion) Hardness D-240 Shore D 65 Melting Point DSC ° C. (° F.) 154 (309) Tensile Strength D-638 MPa(kpsi)  50 (7.3) @ Yield Elongation at Break D-638 % 350 FlexuralModulus D-790 MPa (kpsi) 180 (26) Volume Resistivity D-257 ohm-cm  10¹²

Polymer Example 3

Copolyamide (nylon 6,6-6,6,10) described earlier in Polymer Example 2was mixed with phenolic resin, identified as Georgia Pacific 5137.

Nylon:Phenolic Resin ratio and its melt temperature of blends are shownhere:

Composition Melting Temperature (F. °) Polyamide: Phenolic = 100:0 150Polyamide: Phenolic = 80:20 110 Polyamide: Phenolic = 65:35 94Polyamide: Phenolic = 50:50 65

The elasticity benefit of this new fiber chemistry comes from the blendof a polymer with a polyurethane. The polyurethane used in thisinvention is polymer Ex. 1 obtained from Noveon, Inc. and is identifiedas TECOPHILIC SP-80A-150 Thermoplastic Polyurethane. This is analcohol-soluble polymer and was dissolved in ethyl alcohol at 60° C. byrigorously stirring for 4 hours. After the end of 4 hours, the solutionwas cooled down to room temperature, typically overnight. The solidscontent of the polymer solution was around 13% wt, although it isreasonable to suggest that different polymer solids content can be usedas well. Upon cooling down to room temperature, the viscosity wasmeasured at 25° C. and was found to be around 340 cP. This solution waselectrospun under varying conditions successfully. FIGS. 1A and 1B showa series of Scanning Electron Microscope (SEM) images showing theas-spun fibers along with some functional particles (SEM image).

In the field of chemical filtration, the particles displayed in the SEMimage 1 (FIG. 1) provided above, are activated carbon particles intendedfor removal of certain chemicals in the gas phase. The adsorptioncapacity of these particles has a strong relationship with theirpost-process conditions. In electrospinning, the solvent vapor comingoff from the electrospun fibers as they form and dry can be readilyadsorbed by the carbon particles hence limiting their overall capacity.In order to “flush” the solvent molecules from the activated carbonparticles, it is therefore necessary to heat the structure at atemperature beyond the boiling point of solvent, in this case 78-79° C.,for an extended duration of time, to get any residual solvent off fromthe carbon particles. Consequently, these fibers should withstand theseextreme temperatures during the post-treatment process in this examplepresented above.

To improve the temperature resistance of these fibers and at the sametime to benefit from their high elasticity and tackiness (desired forattachment of active and/or non-active particles etc.), we have blendedthe polyurethane based polymer solution with a polymer solution polymerexample 2 that is a polyamide-based solution

Ultimately, we have used the 48/52% wt blend ratio between polymerexample 1 and polymer example 2, respectively; the resulting solutionhad a viscosity of about 210 cP. The mixing was carried out at roomtemperature by simply stirring the blend vigorously for several minutes.Electrospinning of the blend was carried out using typically process.The as-spun fibers were then subjected to heating; in this case heatingwas carried out at 110° C. for 2 minutes.

The fibers electrospun from this polymer solution blend polymer example1 and polymer example 2 have excellent temperature stability and goodelasticity and tackiness, which are not possible to find all-in-one inany component of the solution, polymer example 1 and polymer example 2.The fibers have an average diameter about two to three times that of theaverage fiber diameter of polymer example 2 fibers (polymer example 2average fiber diameter is in the range of 0.25 microns).

While this polyurethane has excellent elasticity, it is rather preferredto have temperature resistance as well. This is particularly importantif there are subsequent downstream processes that require hightemperature processing.

The polymer solution was as follows: the polymer had a melt flow indexof 18.1 g/10 min measured at 180° C. The solution viscosity was measuredas 210 cP at 25° C. using a viscometer.

Reemay 2011 polyester substrate was used to deposit thenanofiber/activated carbon particle composite. The substrate is veryopen, substrate fibers are laid down flat with no protrusion of fibersfrom the web and has a very low basis weight, 25 g/m². There can be awide selection of different substrate materials suitable for theproduction of this nanofiber/activated carbon composite.

Activate carbon particles were dispersed to the nanofiber matrix using adeflocculator system, where the particles were fed to the deflocculatorusing a dry particle feeder (screw feeder) with electronic controls overthe particle output rate.

The substrate was mounted on a continuous belt (FIGS. 4 a and 4 b) andas such the composite was generated using a pilot machine with limitedfiber spinning capability.

The following table summarizes the run cycle:

Example   0 sec Start of the electrospinning of the polymer solution  20sec Start of the particle deposition 1260 sec Amount of particledischarged is 60 g/ Particle deposition stopped 1290 sec Onlyelectrospinning of fibers from 1260 to 1290 sec/Electrospinning stoppedDescription of the run cycle used for generating the nanofiber/activatedcarbon particle composite.

Quantification of the accurate amount of carbon inside the composite wascarried out. To do that, the same polymer solution was electrospun forthe same duration of time (1290 sec) onto the same Reemay 2011 substrateat the same processing parameters. Later, by cutting the same samplesizes (4 inch diameter), both samples (one with particles and the otherone without) were weighed, and the difference between the two weighingprovided us the activated carbon loading in the given surface area ofthe sample (1 m²), we have calculated that the amount of activatedcarbon inside the composite was 56.04 g/m². In other words, out of 60 gof particle discharged from the feeder, 56 g was able to make it to thecomposite, whereas 4 g was lost in various ways including deposition tothe inner surface of the nozzle that was used to deflect the particletrajectory.

Overall, the nanofiber/activated carbon particle composite was composedof 91.4 wt % of carbon particles and 8.6 wt % of polymeric nanofibers.

By applying the particles in this dry method, we have utilized a largeportion of particles inside the composite, and furthermore the drymethod of application allowed us to not block the particle surface areato the extent that it would effect the diffusion of the challenge gasinto them.

There are two distinct mechanisms of capture of activated carbonparticles in the nanofiber matrix:

-   -   Mechanical entanglement of the particles inside the nanofiber        matrix that inhibit the particles from moving freely inside the        composite. The result is a nanofiber network that acts much like        a spider web, capturing and holding the particles on itself. As        more layers are deposited, the network turns into a nanofibrous        matrix of nanofiber and particles.

Adhesion between the particles and nanofibers as a direct result ofsolution spinning of the nanofibers. Because nanofibers were createdfrom a polymer solution using electrospinning process, as the nanofibersland on the target, they may retain a very small amount of the solventin their structure and hence they have the ability to fuse onto theactivated carbon particles. Because the fibers have very small fiberdiameter, and there are only a handful of nanofibers in contact with theparticle, the available surface area of the activated carbon forchemical adsorption is dramatically high, enough to affect theperformance of the media in a positive way.

The heat treatment at 230° F. for 5 minutes is carried out becauseduring electrospinning of almost any polymer solution there could be avery small amount of residual solvent remaining in the nanofiberstructure. In an attempt to eliminate any residual solvent, which couldaffect the adsorptive capacity of the activated carbon particles, weheated the composite beyond the boiling point of the solvent used toprepare the polymer solution. In this case, the boiling point of thesolvent was around 176° F. at 760 mmHg. And thus heating at 230° F. for5 minutes ensured the complete removal of any residual solvent from thenanofibers and/or the activated carbon particles.

Below is a table that outlines the results of the particulate efficiencytesting conducted using TSI 3160 fractional efficiency test bench withdioctyl-phthalate particles in the 0.02-0.4 micron diameter range, at10.5 ft/min face velocity. Efficiency, penetration and resistance arethe outputs of the testing. This sample was tested after heating it at230° F. for 5 minutes in a lab oven.

Particle Size D (microns) Eff. (%) Pen. (%) Res. (mm-H₂O) FOM 0.02 99.810.19 13.98 326 0.03 99.61 0.39 13.96 289 0.04 99.30 0.70 13.97 258 0.0598.06 1.94 13.98 205 0.06 97.53 2.47 13.98 192 0.07 97.00 3.00 13.98 1820.08 96.47 3.53 13.97 174 0.09 96.04 3.96 13.99 168 0.10 95.50 4.5013.97 161 0.20 95.29 4.71 13.98 159 0.30 97.06 2.94 13.99 183 0.40 98.371.63 13.98 214 Carbon loading g/m² 56.04 Carbon concentration % 91.40Total fiber and carbon composite g/m² 61.31FOM (Figure of Merit) is calculated using these outputs and the facevelocity of the test by the following formula:Figure of Merit=−Ln(penetration)/(deltaP/media face velocity)The standard unit of measure of FOM is 1/(cm Hg)/(cm/sec) or (cm/sec)/cmHg The higher the FOM, the better the quality of the media is; in otherwords, higher FOM means either higher efficiency for the same pressuredrop, or lower pressure drop for the same efficiency.

From the table presented above, one can see that the particulateefficiency of this sample is in the high 90% range. It is verystraightforward to generate composites with even higher particulateefficiency by several means:

Increasing the thickness of the overall composite

Keeping the thickness of the overall composite the same, however, addinghigh efficiency layer made of very fine (around 0.25 micron) nanofiberscoated on the bottom and top of the nanofiber/activated carbon particlecomposite

The second method is preferable, simply because it would allow keepingthe chemi-adsorptive properties of the composite the same, while theparticulate efficiency can be adjusted independently.

The application of this invention is to purify fluid streams, includingliquid streams and gaseous streams. The filter element of the inventionis placed in a location or environment suitable for a particularapplication, such that a contaminate-laded fluid stream can pass throughor pass by the element, and contaminates can be removed. Fluid streamsfor the application include liquid or gaseous streams that can containcontaminates such as dust particulate, water, solvent residue, oilresidue, mixed aqueous oil residue, harmful gases. Mobile liquid streamsinclude fuels, oils, solvent streams, etc. The streams are contactedwith the flow-through or flow-by structures of the invention to removeliquid or particulate contaminants, color forming species, and solubleimpurities. The contaminates to be removed by application of theinvention also include biological products such as, for example, prions,viruses, bacteria, spores, nucleic acids, other potentially harmfulbiological products or hazardous materials.

In aspects. the invention can be used to purify fluid streams, with somefurther addition of liquid filtration including fuel and lubes, waterfiltration.air streams in any application that requires airborne acidic,basic and volatile organic gaseous filtration at relatively low gasconcentrations (<100 ppm). The application environments may consist ofeither a stagnant or flowing gas stream that is either dry or containssignificant amounts of water. One of the primary applications for thisinvention is to have a light weight, low pressure drop adsorbent mediafor semiconductor applications that require purified air to be providedto a process, tool, test, or enclosure. This may include otherapplications that require purified air, nitrogen, or other process gasstream. The adsorbent media is capable of removing gaseous contaminationwithin clean rooms, semiconductor industry or sub-fabrication system,process tools, and enclosures through single pass, recirculation, orstatic filtration. Additionally, the media can purify air that is takenfrom one location to another. Such air transfer can be from asub-fabrication to the main fabrication, or from the external atmosphereto an emission test system.

In one aspect, the filter element of the invention can be placed in avent for an enclosure, such that the interior of the enclosure ismaintained at a substantially reduced moisture content with respect tothe exterior of the enclosure, because the adsorbent media removesmoisture from the interior of the enclosure. The enclosure in which thefilter element is placed includes an enclosure containing an electroniccircuit or device, wherein the electronic circuit or device includes,without limitation, an organic light emitting diode, a hard drive, adisplay, or some combination thereof. For example, the filter element ofthe invention can be used as a moisture-absorbing flexible display foran electronic device. The flexible display comprises a lighted display(including displays formed using light emitting diodes) combined withthe filter element, which absorbs moisture from the environment orenclosure in which the flexible display is used.

Depending on the amount of performance necessary, this media could beused in various applications and in various forms including particlefiltration and chemical filtration in the same layer or confined space,combination particle filter and chemical filter for use in a gas turbineapplication, chemical filter as the only option for gas turbine systems,high flow applications in the semiconductor industry for fan assemblies,point of use, and full filter fabrication locations or labs,applications that require a “gettering” type filter, point of usefiltration for semiconductor within clean rooms with minimal space andmaximum efficiency, tool mount filter for semiconductor applicationswithin clean rooms with minimal space and maximum efficiency, high flowapplications in ceiling grids for clean rooms applications, applicationsthat require a reduced weight but similar efficiencies, applicationsthat require a reduced pressure drop but similar efficiencies, locationsrequiring low particle shedding, or layers of chemical filters can beused. Respirators, dust masks, surgical masks and gowns, surgicaldrapes, HEPA replacement including filters for semiconductor processingequipment and clean rooms, sir filtration for gasoline, natural gas ordiesel powered engine, inlet filtration for air compressors, inletfiltration for dust collection equipment, vacuum cleaner filters, acidgas removal from air, cartridges for dryers, CBRN protection materials,wound care, HVAC applications, cabin air filtration, room air cleaner,fuel filter, lube filter, oil filters, liquid filters, air filter forfuel cell application, process filters, insulation material, filters fordisk drives, filters for electronics enclosures, chromatographicseparations, bio-separations can all be made with the materials of theapplication.

By alternately stacking flat sheet chemical filtration with a spacingmedia, this can create flow channels within the element. These channelsallow the gas fluid to be filtered to pass across the media in such amanner as to perform the desired reactions, while, at the same time,maintaining a lower pressure drop than the chemical filtration mediawould allow by itself. The spacing media may be chemically treated toassist in filtration or may be inert.

Similarly, flow channels in a filter element can be created byco-rolling the spacing media and chemical filtration media around achemically active or inert core. This can be seen in the (FIG. 3).

Once the fine fiber layer containing the active or active inertparticulate of the invention is prepared, the layer must be mechanicallyassembled into a useful active or adsorbent or absorbent structure.Nanofiber layers are typically spun onto a substrate material which canbe a scrim, a cellulosic substrate, a mixed synthetic cellulosicsubstrate or a purely cellulosic substrate. The nanofiber layerscontaining the active or inert particulate are electrospun onto saidsubstrates and the substrate can then be rolled into an absorbentstructure. Alternatively, the layer can be cut into similar portions andstacked to form an absorbent layer. It is important that the internalstructure of any assembly of the nanofiber layers has sufficient airflow to ensure that the air can pass easily through the assembly. Inthis case, the assembly would act, not as a filter, but purely as anabsorbent assembly structure. In an alternative structure, the layers offine fiber and reactive or active particulate can be assembled into astructure that filters and reacts, adsorbs, or absorbs. Such varyingstructures have applications in a variety of end uses. The formerstructure has little or no filtration properties and can remove reactivecontaminant materials from fluid streams such as air streams or liquidstreams simply using a flow-through mechanism. The latter structure canremove particulate, and can remove chemical species from a fluid such asair, simultaneously with the filtration operations.

In certain preferred arrangements of the wound or stacked layers of theinvention, the media can be configured for a straight through floweither in a flow without filtration properties or a flow includingpassage through a filter layer. In such a fluid flow, the fluid willenter in one direction through a first flow face and exit moving in thesame direction from a second flow face. Within the filter structure, thefluid may not interact with a surface that acts as a filter or it mayinteract with a flow, may contact a surface that obtains filtrationproperties. Generally, one preferred filter construction is a woundconstruction including a layer of media that is turned repeatedly abouta center point forming a coil such that the filter media will be rolled,wound or coiled. One preferred useful structure is a corrugatedstructure in which the material has a fluted construction. Such flutescan be formed and combined with a face sheet. Once the corrugated mediais combined with the uncorrugated media in the form of a face sheet, theresulting structure can be coiled and formed into a useful assembly.When using this type of media construction, the flutes form alternatingpeaks and troughs in the corrugated structure. In certain constructions,the upper flutes form flute chambers which can be closed at a downstreamand while the flute chambers have upstream ends that are closed to formother rows of flutes. In such a structure, the opened and closed areascause the fluid to pass through at least one corrugated wall to obtainfiltration properties from the corrugated layer. In use, such corrugatedmedia in a coiled assembly provides an intake area for a fluid streamsuch as air. Air enters a flute chamber in an open upstream end, theunfiltered fluid flow is not permitted to pass through a closed downstream end but is forced to proceed through a corrugated layer or flutedsheet to contact either the fiber of the corrugated layer or the activeparticulate to either filter particulate from the fluid stream, or toensure that the material dispersed or dissolved in the fluid stream isreacted with, absorbed, or adsorbed onto the active particulate.

Experiment for Breakthrough Bench System

Organic gas breakthrough tests were performed on all elements withcontaminate of toluene at 50 ppm. A general block diagram of ourbreakthrough test bench design is given in FIG. 5. Breakthrough testswith a residence time of 0.12 sec were carried out to test adsorbenttoluene capacities. The carbon media of the examples was conditionedinside the column (1.5 inch ID) until the relative humidity reached 50%and temperature arrived at 25° C. Then the air containing toluene(generated from a solvent generation system) flowed through the samplebed with a flow rate of 30 Lpm to begin the breakthrough test.

Contaminants were generated from certified gas standards delivered intothe test air stream through mass flow controllers (Aalborg; Orangeburg,N.Y.; or Brooks/Emerson Process Management, Hatfield, Pa.). The relativehumidity was controlled using a Flow-Temperature-Humidity Controller(Miller-Nelson Research, Inc.; Monterey, Calif.); Model HCS-401. Arelative humidity of 50% RH was used for the studies presented herein.The temperature and relative humidity of the air stream upstream anddownstream of the adsorbent bed were measured using calibratedtemperature and humidity sensors (Vaisala; Woburn, Mass.; Model HMP233).The temperature of the adsorbent bed was controlled at 25° C. using awater-jacketed sample holder and a water bath. Detection of the upstreamand downstream contaminant concentration was monitored using a JUM FlameIonization Detector (FID). FIG. 6 is a breakthrough curves for all finefiber entrapment elements tested. Non-impregnated and impregnatedactivated carbons have excellent removal efficiency and life for certainorganic gases.

Since particle and fiber deposition are independent from each other, wecan generate composites that have varying ratios of particles to fibers.We've generated composites that had nanofiber loading of 8-15% wt in thepast, although no theoretical limit exists on these amounts.Consequently, on such structures, activated carbon loading was in 92-85%wt range.

Typically, the process involves deposition of a very light layer ofnanofibers on a scrim for handling and integrity purposes, followed bythe application of nanofiber/activated carbon composite, whichconstitutes the bulk of the overall composite. In the final stage,another layer of nanofiber-only layer is deposited to the top of thecomposite. This nanofiber only layer on the top and bottom surfaces helpkeep particle shedding to almost none, as we have not seen evidence ofthat in the past. They also help boost the particulate efficiency of thecomposite. The structure of the invention includes, a Nanofiber layer, aNanofiber/carbon composite layer, a Nanofiber-only layer, and a Scrim.

Particulate efficiency is one of the key parameters that bring anedge-formed for this type of media. Below are particulate efficiencydata for two nanofiber/activated carbon composites, with the differencebeing their basis weights. Measurements are recorded using TSI 3160Automated Filter Tester, operated using DOP particles of varying size at10.5 ft/min face velocity on flat sheet samples.

Media A Media B Particle Size Efficiency Penetration ResistanceEfficiency Penetration Resistance D (um) % % mmH2O % % mmH2O 0.02 99.120.88 7.77 99.99 0.01 25.13 0.03 98.28 1.72 7.77 99.99 0.01 25.18 0.0497.04 2.96 7.77 99.98 0.02 25.17 0.05 93.80 6.20 7.77 99.90 0.10 25.200.06 92.45 7.55 7.78 99.87 0.13 25.20 0.07 91.16 8.84 7.80 99.83 0.1725.21 0.08 90.09 9.91 7.78 99.79 0.21 25.22 0.09 89.14 10.86 7.78 99.780.25 25.24 0.10 87.94 12.06 7.78 99.67 0.33 25.27 0.20 86.65 13.35 7.8199.64 0.36 25.24 0.30 89.09 10.91 7.79 99.82 0.18 25.28 0.40 91.76 8.247.80 99.93 0.07 25.28 Carbon g/m2 26.38 g/m2 77.48 loading Carbon %85.52 % 84.63 concentration Total g/m2 30.85 g/m2 91.55 carbon + fiber

This table shows particulate efficiencies of two nanofiber compositeswith different thicknesses. As one can see from the table above, byvarying the composite thickness we have successfully changed theparticulate efficiency of the composite. It is also possible to modifythe particulate efficiency by varying the amount of nanofiber layer onthe top and bottom surfaces of the composite without affecting thenanofiber/carbon composite in the middle. Furthermore, it is possible tointroduce one or more nanofiber-only layer inside the middle compositein an attempt to boost the particulate efficiency to the desired targetlevel. Another structure can include a Nanofiber layer, aNanofiber/carbon composite layer, a Nanofiber-only layer and a Scrim.

This Nanofiber composite similar to that above, the difference is ananofiber-only layer in the middle of the nanofiber-carbon compositefunctioning as a particulate efficiency enhancement stage. Whileparticulate efficiency is one aspect unique to this invention, anotheraspect is chemical adsorption and removal of contaminants from gasphase. In an attempt to understand the effects of different levels ofcarbon loading, Media A and Media B, which were tested for particulateefficiency were also tested for chemical adsorption capacity. In thiscase, these media were challenged against toluene. Results show thatvarying the degree of carbon loading affected the breakthrough time andoverall capacity of these media as shown in FIG. 6. Note that thesemedia were tested not in a pleated form but rather in a spirally-windedform and hence the curve should be taken into consideration only forwhat it is intended to be presented for, and not for an actualperformance in a respirator application.

Since particle and fiber deposition are independent from each other, wecan generate composites that have varying ratios of particles to fibers.We've generated composites that had nanofiber loading of 8-15% wt in thepast, although no theoretical limit exists on these amounts.Consequently, on such structures, activated carbon loading was in 92-85%wt range.

Typically, the process involves deposition of a very light layer ofnanofibers on a scrim for handling and integrity purposes, followed bythe application of nanofiber/activated carbon composite, whichconstitutes the bulk of the overall composite. In the final stage,another layer of nanofiber-only layer is deposited to the top of thecomposite. This nanofiber only layer on the top and bottom surfaces helpkeep particle shedding to almost none, as we have not seen evidence ofthat in the past. They also help boost the particulate efficiency of thecomposite. The structure of the invention includes, a Nanofiber layer, aNanofiber/carbon composite layer, a Nanofiber-only layer, and a Scrim.

Particulate efficiency is one of the key parameters that bring anedge-formed for this type of media. Below are particulate efficiencydata for two nanofiber/activated carbon composites, with the differencebeing their basis weights. Measurements are recorded using TSI 3160Automated Filter Tester, operated using DOP particles of varying size at10.5 ft/min face velocity on flat sheet samples.

Media A Media B Particle Size Efficiency Penetration ResistanceEfficiency Penetration Resistance D (um) % % mmH2O % % mmH2O 0.02 99.120.88 7.77 99.99 0.01 25.13 0.03 98.28 1.72 7.77 99.99 0.01 25.18 0.0497.04 2.96 7.77 99.98 0.02 25.17 0.05 93.80 6.20 7.77 99.90 0.10 25.200.06 92.45 7.55 7.78 99.87 0.13 25.20 0.07 91.16 8.84 7.80 99.83 0.1725.21 0.08 90.09 9.91 7.78 99.79 0.21 25.22 0.09 89.14 10.86 7.78 99.780.25 25.24 0.10 87.94 12.06 7.78 99.67 0.33 25.27 0.20 86.65 13.35 7.8199.64 0.36 25.24 0.30 89.09 10.91 7.79 99.82 0.18 25.28 0.40 91.76 8.247.80 99.93 0.07 25.28 Carbon g/m2 26.38 g/m2 77.48 loading Carbon %85.52 % 84.63 concentration Total g/m2 30.85 g/m2 91.55 carbon + fiberThis table shows particulate efficiencies of two nanofiber compositeswith different thicknesses.

As one can see from the table above, by varying the composite thicknesswe have successfully changed the particulate efficiency of thecomposite. It is also possible to modify the particulate efficiency byvarying the amount of nanofiber layer on the top and bottom surfaces ofthe composite without affecting the nanofiber/carbon composite in themiddle. Furthermore, it is possible to introduce one or morenanofiber-only layer inside the middle composite in an attempt to boostthe particulate efficiency to the desired target level. Anotherstructure can include a Nanofiber layer, a Nanofiber/carbon compositelayer, a Nanofiber-only layer and a Scrim.

This Nanofiber composite similar to that above, the difference is ananofiber-only layer in the middle of the nanofiber-carbon compositefunctioning as a particulate efficiency enhancement stage. Whileparticulate efficiency is one aspect unique to this invention, anotheraspect is chemical adsorption and removal of contaminants from gasphase. In an attempt to understand the effects of different levels ofcarbon loading, Media A and Media B, which were tested for particulateefficiency were also tested for chemical adsorption capacity. In thiscase, these media were challenged against toluene. Results show thatvarying the degree of carbon loading affected the breakthrough time andoverall capacity of these media as shown in FIG. 6.

Note that these media were tested not in a pleated form but rather in aspirally-winded form and hence the curve should be taken intoconsideration only for what it is intended to be presented for, and notfor an actual performance in a respirator application.

FIG. 7 shows the performance of a high surface area coconut shell carbonplaced within the web of our fine fiber matrix in acceleratedbreakthrough test for toluene. Although the efficiency breakthroughcurve for 50 ppm toluene for this material indicates it has some initialefficiency and life problems; we believe we can overcome this issuethrough increasing the overall length of the channel as well as newdesigns.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

1. A filter media comprising a non-woven filter substrate and a fiberlayer or fiber web comprising a substantially continuous fine fiberlayer formed on the non-woven filter substrate, the fiber having adiameter of about 0.001 to 5 microns and an active spacer particulatedispersed in a substantially uniform manner in the fiber layer or fiberweb, the particulate comprising 0.1 to 50 vol % of the layer or web andthe layer or web having a thickness of about 0.0001 to 1 cm and asolidity of about 0.1 to 70%; wherein the active particulate comprisesabout 0.001 to 10 kg per square meter of the layer or web, and whereinsolidity of a fine fiber layer without the active spacer particulate isgreater than the solidity of a fine fiber layer formed with the activespacer particulate.
 2. The filter media of claim 1, wherein the solidityis about 1 to 50%.
 3. The filter media of claim 1, wherein the filtermedia comprises a flow-by direction such that a fluid can flow in a pathparallel to the substrate with no filtration path through the media. 4.The filter media of claim 1, wherein the fiber has a diameter of about0.001 to 0.5 micron.
 5. The filter media of claim 1, wherein the web hasa figure of merit of about 10 to 1,000.
 6. The filter media of claim 1,wherein the thickness of the fiber web is about 1 to 100 times the fiberdiameter.
 7. The filter media of claim 1, wherein the layer comprisesabout 30 to 75 wt % fiber and about 70 to 25 wt % active particulatemeans, the layer comprising 1 to 1000 grams of active particulate persquare meter.
 8. The filter media of claim 1, wherein the activeparticulate means has a major dimension less than about 5000 microns. 9.The filter media of claim 1, wherein the particulate is an absorbentparticulate, an adsorbent particulate, a reactive particulate, ormixtures thereof.
 10. The filter media of claim 9, wherein theparticulate has a major dimension of about 5 to 200 microns.
 11. Thefilter media of claim 9, wherein the particulate has a major dimensionof about 0.1 to 70 microns.
 12. The filter media of claim 1, wherein theweb has a Frazier permeability of about 1 to about 50 meters-minutes⁻¹and an efficiency of about 40 to about 99.9999% under ASTM 1215-89 usingmonodispersed 0.78 micron polystyrene particulate at 6.1 m-min⁻¹ or 20ft-min⁻¹.
 13. The filter media of claim 1, wherein the particulate is anabsorbent.
 14. The filter media of claim 1, wherein the particulate is acombination of an inert particulate and an active particulate spacermeans.
 15. The filter media of claim 1, wherein the web has a gradientin the distribution of the active spacer particulate.
 16. The filtermedia of claim 1, wherein the web has a gradient in the distribution ofthe fiber.
 17. A method of removing moisture from an air stream, themethod comprising placing a filter element in a location such that amoisture-laden air stream can pass through or pass by the element, theelement comprising a non-woven filter substrate and a layer comprising asubstantially continuous fine fiber layer formed on the non-woven filtersubstrate, the fiber having a diameter of about 0.001 to about 5 micronsand comprising an active spacer particulate dispersed in a substantiallyuniform manner in the fiber layer, the particulate comprising 0.1 to 50vol % of the layer and the layer having a thickness of about 0.0001 to 1cm and a solidity of about 0.1 to 70%; wherein the active particulatecomprises about 0.001 to 10 kg-m⁻² of the layer, and wherein solidity ofa fine fiber layer without the active spacer particulate is greater thanthe solidity of a fine fiber layer formed with the active spacerparticulate.
 18. The method of claim 17, wherein the element is placedin a vent for an enclosure such that the interior of the enclosure ismaintained at a substantially reduced moisture content with respect tothe exterior of the enclosure.
 19. The method of claim 17, wherein theenclosure comprises an enclosure containing an electronic circuit ordevice.
 20. The method of claim 17, wherein the electronic circuit ordevice comprises an organic light emitting diode.
 21. The method ofclaim 17, wherein the electronic circuit or device comprises a harddrive.
 22. The method of claim 17, wherein the electronic circuit ordevice comprises a display.